Also, some information coming out of smashboards.com
This information was dug up from two different japanese magazines, and translated by Samurai Panda.
1) The voice-actors for Ganandorf, Marth, and Roy have already worked on Super Smash Bros. Brawl, hinting at their return in some form or another.
2) (This one is clearly stated as a rumor) Brawl will be delayed again, according to internal sources.