I've been reading a lot of posts talking about how clementine should be the next playable character. Not only is this not possible due to the time jump needed for clementine to be of an age(not that i have anything against playing as children) where she can be truly bad ass because the comics aren't that far ahead yet. But it would also make the entirety of season 1 pointless. The whole of season 1 has been giving clementine life skills and pointing her in the "right" direction depending on your choices. Giving her own opinion on how she likes things done and then making her controlled by the player would make any decision made as lee(think stealing from the car) pointless.
If Clementine was too appear in season 2(which i'm doubtful she will) she would be better off as a Kenny/Lilly character who will side with you or hate you dependent. Just my 2cents
P.s clementine will totally die at the end of season 1 if you fuck it up