It'll be hard to replace a legend. It's like Drew Carey replacing Bob Barker. IMHO, I don't think Drew Carey is a good host. He looks nervous all the time. But I can imagine they will have guests hosts for a while until they figure out who would be the best.
I like the idea of either a former successful Jeopardy contestant (Buzzy Cohen for instance), or, someone completely new and unknown but who has gravitas. I don't want to see any "celebrity" as host of Jeopardy.