Its time for someone to declare the elephant in the living room: Dick Clark needs to hang it up.
Recovering from a stroke is not an easy task. You literally have to re-learn how to talk. However I don't think its necessary to mark someone's recovery by carting them out on camera every year simply because its tradition. Let the man retire and keep his slurring, near drooling half-numb ass off of television. He's done enough.
If I want to hear someone slur their speech, I'll go to a party and hang out with the drunks. They're usually more fun anyway.