I hope the r&b scene isn't dead even if i haven't attended an r&b or mod night in quite a number of years now. Personally i felt the quality of the new records getting played was diminishing which is why i strayed, (and also my tastes changed) but i wouldn't like to hear that scene was falling on hard times. I read on here loads of threads regarding r&b records, both new discoveries and old faves, so at least from a collecting and online point of view it seems to still be thriving?
I'm not so sure i would want to hear r&b records mixed in with 70's and crossover though. The form of the styles have too many disparities and i don't think they would sit will together. This of course is generalizing, the right soulful r&b/r&s record can sound great in amongst later 60's stuff (and that is often the case) but i think very early Big Mama era r&b and early popcorn sounds (regardless of a personal dislike for the latter) would make for a muddled night of music....
I get the impression that there are also plenty of soulies who are big fans and collectors of r&b, i think this 'big divide' is often overstated. I think you'd be hard pushed to find soulies who couldn't see the merits of 45s like Carl Underwood, JD Abram, Delores Johnson, Leroy Harris ect....