Peach will be returning, she is way too important to the Mario series.
I'm a Ness fan/user, but I won't go psycho like I did on the last person who wanted Ness booted. I was sick that day. To each their own. I'm starting to think the Ness debate could go either way. On the plus side, he was one of the original twelve, which people have indicated is a strong sign. On the other hand, some think he could be replaced a by a new Earthbound character known as Lucas.
PopFusion, did you know Peach was intended for the original SSB, but there was some sort of complication so she (along with Bowser and Mewtwo) wasn't included?