No, unfortunately it's the opposite, they (we) will become more and more TJ-ish with age.
I agree. I can see that especially with ENTJs like Napoléon, Marlon Brando, Angelina Jolie, Alain Delon or Matt Damon, when they are younger they seem to be more in touch with their ISFP shadow: wild , romantic, sensitive, fragile, facetious, joking. But as they age they seem to move to a more unidimensional ENTJ style: touchy, cold, controlling, rigid, ambitious, visionnary.
It's especially true for the middle ages ENTJs, I think. A stressfull lifestyle, with a lot of responsabilities make the ISFP shadow useless, and the ENTJ style more necessary. The eldest ENTJs though, seem to reconect and be more in touch with their inferior Fi though, as they retire.
EsTP 6w7 Sx/Sp
E=60% S=55% T=70% P=80%
"I don't believe in guilt, I only believe in living on impulses"
"Stereotypes about personality and gender turn out to be fairly accurate: ... On the binary Myers-Briggs measure, the thinking-feeling breakdown is about 30/70 for women versus 60/40 for men." ~ Bryan Caplan
I'm not an NT but my observations suggest that FP become more TJ with age but TJ become more TJ. In the end Te is too damn useful a function and the more you train its use the easier your life will become. That's not to say that they won't necessarily train their FP functions. Fi is more useful as a supporting guide rather than an invisible hand. Although it isn't good at management or business (it can even be detrimental at times) a developed Fi as a known and understood quantity won't screw them around half as much as a subconscious Fi which is screaming out like a virtually inaudible white noise undermining their tactics or strategies without them ever knowing why.
But that is for the working TJ. A retired one will find time to relax and lazy days to take things slow.