It always has been, so it would be a pretty wild change if they no longer were.  It's possible though.  Most algorithms now have ASICs and if they don't then ASICs or FPGAs can still be created rather quickly to take advantage of anything new.  That certainly puts GPUs on the back burner.  However, with AI being a massive user of GPUs I would think an obvious solution to this would be a blockchain that somehow powered AI creations using GPUs.  If something like this gets created, I could see it's coin being an extremely valuable to "mine" asset.