I only hope they don't "force" her to be in a game as Drew was, and just keep her at the desk as Clive was. I didn't know Aisha Tyler until she showed up on Talking Dead last night, but she seems quick enough to host.
No slight to Drew - he's a great host, but his background is in standup. Without getting too deep into the theory of improvisation, in standup you are in solo control on stage, whereas in improv it's about relinquishing control to the team and the scene. And it showed - Drew was only ever playing Drew on Whose Line, even in the later seasons when he was endowed with a character. Speaking from experiencee, I know it's MUCH more fun to improvise with someone who's actually IMPROVISING. If you dig up some of the later improv stuff he's done (Green Screen Show, Improvaganza), Drew is MUCH better at it.
Drew's chemistry with the gang was great, but the playful antagonism was doubtless rooted in the differences in background he had with the trained improvisors he hosted. I hope Aisha can use her own background to get laughs as a result of improv rather than just watching her screw up on stage as Drew usually did.