The best Doctor Who of the recent set was David Tennant. Matt Smith has been playing the part for a while now and it's time for a regeneration. But who better to be Who than David Tennant?
We believe the showrunners should consider something innovative and surprising for the continued 50th Anniversary celebration--a retro-regeneration. It's never been done. But we haven't found a reason WHY not in the Who canon.
It could be entirely brilliant to have David Tennant return as Doctor Who. In fact, the last line uttered by him was, "I don't want to go". We didn't want him to go either.