They won't ever crash, but they could easily decline severely in popularity as they rely mainly on CoD. CoD goes, FPSs become way smaller. They'll still be big, so not "crashed", but nothing compared to before.
If FPS does somehow crash, other popular genres will eat into it, mostly other "kill kill kill" kind of games, probably.
“These are my principles; if you don’t like them, I have others.” – Groucho Marx







