There were rumblings of a Lucas spin-off from House a long time ago, and though that idea has since been nixed, don't count out the possibility of seeing another character lead their own series. Fox president Kevin Reilly recently confirmed that exec producers David Shore and Katie Jacobs have a "standing offer" to create another show, possibly a spin-off.
This begs the question: if Lucas doesn't get his own show, then who should? I find Wilson completely lovable, but I'd hate to break up the bromance. Perhaps Cameron? There have been hints that she's coming back, so now seems like the right time, but honestly I just don't find her interesting enough to carry a show on her own. Thirteen could carry her own show; at least she has a more intriguing backstory. I wouldn't mind seeing Cuddy segue into new territory either. We could follow her as she starts a new life with Lucas in a different city, and at least it would put to bed those tiring "will they/won't they" storylines with House.
Or not. Hey, that's what crossover episodes are for.
Here are my top choices for a separate series — who gets your vote?