Several things; in terms of human evolution stalling, it's hardly the case, even int he last few hundred years we've seen substantial changes, for example, those of us who live in north america are primarily derived from europe... thing is the europeans we descended from were on average about 8-10 inches shorter. In other areas, such as sweden, height has vastly increased, even within the last few generations alone, children are on average a full foot taller than their grandparents these days in that locale.
Now, that being said, we can move onto biological enhancement; obviously this's being done already. Within the last little bit we've even just recently developed in canada, a way to transform fat cells into behaving as stem cells, which will suddenly allow stem cell research to progress at a rapid pace with easy access to material (liposuction for science!), and note that this process actually is much faster (2 weeks growth time) than the older method of 'real' stem cells (2-3 months). With this, being able to correct things like spinal cord injuries shall likely become very simple to do in the near future.
Next off, we can move onto the technological aspect of immortality... computerized backups of ourselves. This may sound to be in the realm of science fiction, though it's actually probably only maybe 40-50 years off. We have alot of far more complex technologies available than most people're aware of. Things like multistate transistors could revolutionize the processing speed of computers many times over, where 1 bit could contain as much information as 2-3 current ones, but be able to transfer that information at the same speed as a standard binary bit, which would allow for sending information to be far faster in theory than even the human brain is capable of, as our brains operate in the standard binary method for the most part with some exceptions. With far more research being done into neural links and growth, (there was a study done recently which used a rat's neurons on a petri dish to control a robot through electrical impulses, and showed growth and stimulation at learning) it really literally won't be very long before a brain will be capable of interacting with a computer directly. The 'computers' that will be used for this, however, will most likely use newer technology which's being held back from mainstream computers due to incompatability issues (such as multistate transistors), since whot works in a computer NOW is neccesary... we've boxed ourselves in technologically when it comes to computers, since we can't allow all our previous data and programs to become obsolete with the advent of newer, more advanced technology, so many of our current 'better' technologies in the way of computers, are off collecting dust, because they can't be made to work with the stuff we have right now. That being said, if we weren't concerned about having these interact directly with our current computers, (ie we're only using them to store information on brain data) then the progress to this end is far closer than one would expect compared to a traditional PC or laptop. It's estimated this'll take approximately 40-50 years at this point, but a few random breakthroughs could push this timeframe much faster unexpectedly.
Lastly though, we do have the religious aspect in and of itself. For the desire to make oneself better physically? Of course, why wouldn't we? It only makes sense to, and to be perfectly blunt, the people who're insistant on the silly notion that "we should not play god", have no clue whot they're talking about. Even in most of the holy texts, such is actually ENCOURAGED.
For example Matthew 21:18-22, which can be easily interpreted to be the prediction of the advances of technology and potentially psychic powers (which honestly does sound a bit science-fictionyish, apparantly that genre's been around for longer than we thought).
There's a fair number of these types of passages however, which state that humans will one day be nearly on par with God himself, now whether these are just "we like to think we're better than we are", or if they're more substantial, who knows, but we are in fact headed that way rather quickly.
All things known considered, we can at least state that human nature is to improve oneself, one's environment, and manipulate all things around and within us to better service our own desires and ambitions. As it is literally our very nature to change ourselves for the better, with whichever means and tools we have neccesary, this kind of development along these lines should be viewed as in fact natural to us. It's no different than a rock, a bow, a car, et cetera. To go against this would be to take the amish's point of view, and really there is literally no difference here at all. The line being drawn is not a solid line, it's not even a thin, or dotted line, but completely imaginary to match their own pretensious beliefs.
Now, that being said, there will always be those who resist change, change and difference is scarry, fear of the unknown, fear of things yeu don't understand, fear of becomming 'less' than yeurself, or 'less human'. There is the possibility that such could occur, in the early stages of development, unfortunately. There are strong possibilities that the first few prototypes of such could lock one's mind forever in static process, never able to learn or become better... trapped to never be more than it once was. Which would keep yeu literally the same as yeu were, yeur personality intact, and yeur mind identical, with no risk of the growth that instill such fear.
However, later iterations, where the mind can continue to expand and learn, grow and prosper, for centuries... can teach us much as well.
There are problems on both sides however.
A short lifespan can give way to new ideas and methods of looking at things. See even those who are elderly today, their minds do not grasp new concepts in nearly the same level of ease, new ideas and ways of thinking of things are often far too difficult... rapid generations with advanced education can learn quickly, and make new and better use of the technology learned.
At the same time, however, this is a double edged sword, and it does very much so swing both ways. In this case, we also have the issue that a longer lifespan, leaves more time TO learn... consider if da vinci existed today, with the total culmination of all information up to this point, whot could he do with it? The capacity to see new information and correlate it to older information is important, as is the differing perspectives... by always changing to a new generation, we also deprive ourselves of older perspectives, which may have provided a wealth of knowledge that is now overlooked due to the differing methods.
Then again, we can go back to the first once more. Without short lived generations, true progress can never occur either. Think of the quote that "it takes 20 years for a liberal's ideas to be considered conservative thinking". A generation being roughly 20 years, each new generation tends to imply new ideals, and understanding. 20 years from now gay rights will probably be an assumed concept and those who were against it will seem as quaint and foolish as those who barred black's rights, women's rights, and so on. Only by removing the previous generation from the picture, and placing a new one which had to learn through it, will we progress fully.
If we *DID* suddenly, and magically, create immortality... consider the ramifications it would have socially. We would cease our progress as a whole. Liberal thought would be flattened, and conservative views would hold too much sway... currently we're at a healthy medium; liberal thought creates new ideas, but is tempered by conservative mindset to prevent waste and limit offshoots into worthless endeavours. To heavily overbalance one side or the other is to invite disaster, as both must be maintained.
So although I don't think we're too far off from developing a form of immortality, I do however believe that we are NOT ready for it just yet. The social structuring which would be required to impliment it properly, without destroying us as a whole, is dangerous, as it's going to cause riots no matter whot yeu do. It could be the single worst thing to happen to civilization as a whole if improperly handled, and considering most people won't know how to handle it, and the ones least capable of handling it will be the ones most likely to be in charge of such... well... we'll see how things go, but I can't see it going over too well sadly.
