Pretty much. The only spinoff idea worth anything was Caprica (in part because it originated as an idea for an original series), and we saw how that turned out. Ron Moore's Battlestar Galactica, like Babylon 5, Firefly and Farscape before it, is not well suited to franchising in the way Star Trek is - that it closed its big conceptual loop and answered the probing questions of its universe could leave any prequel series - and it'd almost certainly have to be prequel - feeling a bit redundant. It's best to just wait for the next thing. Maybe Defiance (which has a fair number of ex-BSG writers and Bear McCreary) could become that. Or some other show.