Why though?
Seriously?
Why didn't we cuts in Melee then? Why is it now that we're suddenly going to have cuts on our hands? We had cuts in Brawl because of what little time they had to work on the game. They over estimated themselves and had to pay for it by getting rid of some of the lower priority characters (I mean the reason why we had more characters in Melee is because of how much extra time they had after completing the main cast).
Why do you think Sakurai is being very open about telling us that he can't promise every Smash character returning? It's because, while he doesn't want to make the same mistake again, he's warning us if he can't succeed in saving each character(Which he is obviously trying to do).
From what we can tell, he's not letting the 3DS version hold him back. As we already know that the 3DS Version will release after the Wii U version (and we're seeing that the Wii U version has higher priority for characters being done. As Wii Fit Trainer, Villager, and Olimar didn't have 3DS Screenshots until weeks after they were revealed). They've had a great amount of time to work on the game so far and they still have another year to work on it. Without anything like the Subspace Emissary to worry about, there shouldn't be an issue bring back all of the veterans (ESPECIALLY because of the fact that they don't have to make so many random enemies).
Cuts are by no means going to happen for sure. The only possible cut is Snake because of potential licensing issues with Konami. But even then, why would Konami not want free marketing of their franchise?
If you undoubtably think that there will be cuts, you've got no faith in Sakurai and his team.
"We don’t have the time to fully recreate every single character who’s been in Smash Bros at this point," Sakurai explained.
"Adding new characters is not a simple addition – it’s really multiplication. The amount of work, adding a character is multiplied and becomes bigger and bigger as you go. We can’t because of the amount of work it takes. However, I do believe I understand that each character has its own set of fans out there who really like that character.
"So we’re not going to cut characters out of the way, we’re going to put in as many characters as we can, we really want to do that, because it's good for the fans and good for all of us. But in the event that we do have to cut some characters, I’d like to apologize in advance to those fans."
- Sakurai
Because there were only 12 characters in Smash 64.
The 3DS version has not been confirmed to come out after. The 3DS version is the basis of the game's creativity. It's false logic to assume less screenshots means later release. It could just because the Wii U version looks prettier.
They will have had less time to develop then they had in Brawl.