Do the addition of Mega Evolutions mean that any Pokemon who gets one will never get a standard evo in the future?

I mean, yeah, most Megas are of already 3 stage Pokemon, or they're Megas of Pokemon who are already powerful as it is and don't need a new evolution (Scizor, Heracross).

But what about Absol or Mawile? Bannete or Medicham? Will they now never get a permanent evo?