1.) The disparity in economic growth will remain more or less the same. This assumption can be invalidated through modern observations. For instance, Japan was growing much faster than us in the decades following WWII, and then stagnated so that we were growing faster than them since the nineties. In another example, North Korea developed quicker than South Korea for a while, then the South exploded while the North stagnated and then declined. There are countless other examples (both modern and ancient) to indicate that this assumption is simply erroneous.
2.) That countries with rapid economic growth will have the will and capacity to "rape" other countries to such an extent that a theoretical decline in relative gains will result in less utility for the weaker nations in the long run than an increase in absolute gains. This assumption has far more historical support, but there are some very good reasons why Realism is no longer as highly regarded as rival theories of international politics within most political science departments today. In any event, this assumption would be no reason for weaker countries to (futilely) prefer the status quo unless your first assumption were correct (which it isn't).