Wouldn't it be better to wait for the game to come out or something? o.o
It's not like we know much about Mephiles. Unless we talk about the spoilers of the leakage and such.

But you can see him in one screenshot in Sega's site (dunno if it was the japanese or the english one) where he's talking to Silver and Blaze. He looks exactly like Shadow, only gray.
Will he be misleading them?

as this is already being discussed in this topic, there's no point in creating a new one.