The kha'zix Q nerfs won't stop him from evolving the skill first in almost most situations.
I'm not arguing that kha'zix isn't OP. He's overpowered and that's pretty much a fact.
But Kha'zix right now still evolves QEW/r except right now R is useless if not evolved first. It's a meme among kha'zix mains to show how bad it is. (I know that LCS'zix goes QWE but that's because you can rely on your team in LCS but you can't in Soloqq.)
Now the question is, Does kha'zix evolve Q first because the other evolutions suck or is it because evolve Q is too good?
The answer?
Neither. It's because of the 4 seconds cd on base Q. That's why. After Qing you have to sit and afk for 4-2.2 seconds (Depeding on cdr) waiting for the skill to come back up while you get pounded. The other evolutions are good, but Q is the one that fits kha'zix's play style the best and allows him to kill stuff. Right now, if you decide to not evolve Q, you lose the following:
Faster clear Objective control (Blue buff, Red buff, Dragon) 1v1ing ability Damage Cooldowns
If you do decide to not evolve Q you get the following: more map leverage more slows
Not evolving Q is just loosing too much damage and in a damage heavy meta there isn't much else to say.
TLDR: Kha'zix will still evolve Q as long as the CD is 4 seconds. The solution? I don't know.