2015 - mixed bag, I don't think Winston or Mariota have taken the leaps many had hoped they would...in real life and in fantasy.
2016 - hopefully Wentz and Goff continue to grow, I think if they both have a good 2018 (if Wentz comes back healthy)...they will surpass Winston and Mariota (if they haven't already).
2017 - big year for these 3 guys, can Watson stay healthy and continue what he did in 2017? Can Trubisky take the next step? Is Mahomes actually good?
There may be "talent" incoming at the QB position but it also may be too early to tell...it'd be great if all of these guys were viable and will fill in nicely for the potential retirees but pragmatism will say that a certain percent won't pan out.