The lack of hope has more to do with the nature of Hollywood and TV than anyone's specific lack of desire to try.
James Marsters said that he'd only play Spike for 5 more years after the end of Buffy (or Angel) - and I think we're closing in on that now. SMG, afaik, isn't interested and all the others have moved on to other things - whatever they may be.
A good chunk of folks who'd appeared on BtVS have been on House, MD - Clare Kramer, Tom Lenk, the guy who played Warren (forget his name), Michelle Trachtenberg - and a couple others that I can't think of right off. Plus, countless other things around the TV screens.