If Sonic got a second character, I'd willingly shoot myself.
But seriously, it's not that simple to just say "Hey, Sega...we want Sonic and Knuckles." Those are Sega's characters and Sega has every right to say "No, we don't want you to have them." And yes, I know they have the (
) Mario and Sonic Olympics but they doesn't automatically guarantee two Sonic reps in Smash. As well, I imagine there is a lot of red tape and documents that have to be authorized and signed before a OK is given (and trust me. It takes a LONG time to get **** done in Japan. Everything has to authorized, signed, re-authorized, reviewed, passed around the office, interrogated, re-re-reauthorized, re-drafted, signed again...you get the point. It takes quite some time. Why do you think Sonic came so late into the game?
As well, I am pretty sure Nintendo wouldn't want to include two characters from the same franchise. Maybe the same company but, to me, it's overkill to include two from the same franchise. That also includes:
Snake and Raiden
Megaman and Zero
Pac-Man and Ms. Pac-Man
Ryu and Chun-Li
Why does that company get preferential treatment over another company? Doesn't make any sense. So yeah, I highly doubt a second Sonic character get's in. If, by some grace of God, one does.....it's been nice knowing you.
And KOS-MOS would be boss in SMash. I'd totally want her in.