According to the AV Club
, no one else wants to do it.
Now, that article does cite Neil Patrick Harris as a possible choice, but while I know many geeks would love that, let's be honest: he's done two pretty small movies. He's Emmy hosting material, no question, but not Oscar material.
Besides, unlike NPH, Shatner is pushing 80, and won't be around forever. And when he passes, you know what we're all going to say? We'll say that we wished we'd spent more time with ol' Bill.
Shatner + Oscars. Let the movement start today!