Well, for one I don't think that's ever been said. For two, of course Stardock won't put forth the effort. They're just the publishers. Ironclad is the developer.
I've certainly never seen it said that Rebellion is the end. But as far as SD putting effort in, look who's responding on the forums more often...
Which has me vaguely interested. DO you happen to know if there have been any clues about what this project is?
The only thing I'm completely sure of is that it's not Sins. Do recall something about it being ground-based, however.