Have you guys ever played a punch out game?
No, but that's not relevant.
I'm dead serious. Love Tingle.
I've played Punch Out, I've also played SS, and I would say he's more wanted than Ghirahim, but Ghirahim's moveset potential kind of destroys Little Mac's. Personally, I prefer Ghirahim, but I think Little Mac is probably more likely to be added.
The only reason Mac has a higher chance is 'cause Ghirahim has had limited appearances: one Ninty game generally means said character is a no-go for Smash. Even Sonic 'n Snake had multiple appearances on the Big N's console(s).
I'll instead argue that Sakurai ain't interested in joke characters. Or fighters that ain't of huge repute amongst Nintendo franchises. Tingle is somewhat popular (much to my confusion), but I certainly don't see 'em gettin' in.
Ghirahim is far more likely then Little Mac.
Just let me live in my own little world with this one. =w=