Respectfully, Minigiant, I do not see this logic taking into consideration the 5th edition emphasis on storylines. At the time of the 5th edition roll out, the design team (Mike Mearls, Chris Perkins, Jeremy Crawford, for example) were very clear that the emphasis is moving Dungeons & Dragons forward with storylines, rather then rules options and supplements. The rules options and supplements are published when they are ready to go, but the vacuity or fecundity of the game is not judged by the people making the game based on this rationale of "ideas that can fit in the current race, monster, and class systems." That would be an appropriate standard for 3rd or 4th edition, whose design teams held a different set of assumptions.
Also, I think that when it
does come to rules, there are many areas of expansion and adaptation that go well beyond subclass and monster and even class design.
But, I have made my prediction. We'll see how it goes. Keep 'em rolling!