it is not unova region that was unpopular, it was best wishes anime serie and the stupidity of writers to turn ash dumber and weaker than his kanto beginner (pewter badge) self.
whatever, yep, ash will never use mega, it is obvious now.
And the reasons why he doesn't use it: because ash is an underdog. underdogs don't obtain badass rare item allowing strong power.
There is nothing that would prevent Ash from getting a Mega in a later generation. Also you contradicted yourself, you said that Ash is an underdog, and that because of it he can't obtain badass rare item allowing stronger power( or get a Mega Evolution), which there are holes in your logic, because if what you say is true then explain why Ash has Ash-Greninja a pokemon that is at least as strong as a Mega Evolution, if not stronger. By your own logic Ash shouldn't even have Ash-Greninja, which would mean since he does you can't classify him as an underdog.
The problem with this whole Ash can never obtain a Mega Evolution logic, is that every argument that is presented that says he can never obtain one is flawed for many reasons. In the end there is nothing that will truly stop him from getting a Mega and saying that he will never get one because he didn't get one in the generation it was introduce is like saying he would never get a specific type of pokemon because he didn't get the type of pokemon when it was introduce.
Will Ash obtain a Mega Evolution in gen 7? maybe he will, maybe he won't I don't know, but in no way can it really be said that he will never obtain a Mega Evolution, because we don't know. Plus this whole argument that Ash can not obtain a certain pokemon because of "x" reason has been used before and been proven wrong before, for instance before gen 4 some people would have said that Ash will never obtain a Dragon type pokemon because there too strong and yet in gen 4 he caught one, before gen 5 some people would have said that Ash would never obtain a Dark type pokemon because there too evil looking or some other reason and that he wouldn't obtain a Rock type pokemon because it doesn't suit him or for some other reason and yet in gen 5 he still got a Rock type pokemon and 2 Dark type pokemon.
Before Gen 6 some people would have said that Ash could never have a fully evolved Dragon type pokemon or Pseudo-legendary pokemon because there too strong and yet in this generation he has gotten 2 fully evolved Dragon type pokemon and one of them is a Pseudo-Legendary pokemon. And the list goes on
Basically no matter how many times you try to say that Ash can never get a Mega Evolution it's simply not true, and something that no one can say for sure if it will or won't happen, and all the reasons that you may try to come up with as to why he would never obtain a Mega Evolution wind up being flawed.