Would it be possible to change the protocol so asics couldnt be used? 
From programmers point of view, it can be done in one day of work. It's really THAT easy. But it wont happen, as ppl that OWN ASIC production companies are in control of code creation and they will never let it happe, as that would mean that all their work and investment turns to dust in a second.
And that last part is why i think that Bitcoin REALLY lost it's "decentralization". I hope everyone realizes it sooner than later.
Do i think Bitcoin will die because of it? No. It can not die because of only 1 problem
Do i still believe in bitcoin? I do.
Do i still use it? I do.
Will i buy even more? I will.
I still beleive in Bitcoin and what it could be. Bitcoin can still be really great thing, but we must take it for what it really is, not for what it wanted to be long time ago.