So this might be out of then blue, but I think I've got an okay guess over a new character that I speculate will be in SSB4. Namely, one from the Kirby series.
What character would that be? Waddle Dee. Let's look at some clues:
-Kirby's Return to Dreamland enabled Multiplayer gameplay that let you switch between four different characters... Kirby, Meta Knight, King Dedede and Waddle Dee. The first three are already in SSB Brawl and it's safe to assume they'll all be in SSB4. Kirby's Return to Dreamland was released AFTER Brawl.
-In Brawl, up to four characters (maximum) from one video game series were included (SSB4 has FIVE characters fro