The only reason it's unlikely is because of the publicity backlash that would surely follow any move by Lucasfilm to do so. Legally, there wouldn't be jack any of us could do about getting shut down and our stuff rereleased by Lucasfilm, because this is all (theoretically) a breach of copyright anyway.

But Lucasfilm couldn't afford the publicity: George Lucas, corpulent and successful filmmaker, steals fanboy's ideas for his own? He'd be a laughingstock professionally and in the public's eye. Plus it might bring on a reaction from various entertainment industry guilds against him...