No, Nintendo has not announced that there will be another Smash Bros. - in fact, they've come closest to announcing the opposite.
However, it's still fun to think of characters that should be in the next Smash Bros.. The rules here are fairly simple: the character must have appeared on a Nintendo console as a major character. That's it: the character need not be a Nintendo character, and in fact, by now, probably shouldn't be since Nintendo has kind of hit the bottom of the barrel when it comes to new characters.
- Amaterasu (Ōkami)
- The wolf god with celestial brush powers. Recovery move would have to be Greenspout Vine.
- Waka (Ōkami)
- As a secret character, of course.
- I mean, come on. Throw in Roll as an assist trophy, and combine with Rush for the Final Smash.
- Megaman X
- If we're going to throw in Megaman, we might as well have his older brother, X. I'm not sure that X should really be another character, though.
- Zero (Megaman X)
- But Zero would also work really well as a Smash character.
- Cecil (Final Fantasy IV)
- First a Dark Knight, then a Paladin. I'd say his Paladin form should make it into the game.
- Cain (Final Fantasy IV)
- The Dragoon from Final Fantasy IV.
- Sora (Kingdom Hearts: Chain of Memories)
- Sora was on a Nintendo platform. Technically. His Final Smash would have to be Final Form.
I'm sure I'll add more later, but those are the ones I've thought of so far.