OK, I'm finally going to say it. After extensive research, I've come to the conclusion that the Grinch Leak makes some logical sense, but only with a few characters for one reason;
Sakurai said himself that the licensing was a nightmare.
This seems an odd detail, but hear me out.
For instance, look at Snake. Konami let Nintendo use him in Brawl, so could have simply recycled the agreement. However, the introduction of Castlevania into Smash brings a ton of licensing issues. I mean, two characters, a stage, a few ATs, and 34 tracks?
Now, look at Capcom. They've licensed out Ryu and Mega Man already, so Ken wouldn't be too hard to sort out as an Echo, but more paperwork.
Next exhibit; Sega. They've seemed really into adding reps to Smash, being Sonic and Bayonetta, so Shadow is pretty plausible as another Echo... but more paperwork.
Next; Square Enix. The agreement for Cloud, Midgar and tons of FFVII music is probably extensive, so Geno would realistically be able to be squeezed in too, but more paperwork.
Obviously Golden Sun, Rhythm Heaven and Mach Rider are owned by Nintendo, so not really supported by this.
Lastly is Banjo-Kazooie, owned by Rare... MUCH more paperwork.
I'm thinking that the likelihood of inclusion for the third-parties will be as follows;
1. Shadow
2. Ken
3. Geno
4. Banjo-Kazooie.
This is based on the track records of the actual companies, and the fan service factor, but is just a hunch, really. It's not a leak or anything, just an idea. We'll have to wait and see... Won't be able to sleep tonight for Smash Direct...