I imagine Bruce would've gone back to session work, with Carl starting a group similar to what you stated (or maybe even doing some session work himself). I figure Brian would've taken it as an opportunity to produce Redwood and any other groups he was interested in working with. Maybe Dennis would've immersed himself more in the whole Manson dealio. I'd like to think Al would've tried to start a folk-type project; Mike would've obviously become Paul McCartney's main co-writer after the India trip.