While I like the idea in general of the more kernels, the merrier, part of me can't help but feel that the BSD groups are reaping what they sowed. BSD split for various reasons which seemed more related to being "pure", so to speak, than to fundamental incompatibilities, preferring to be kings of their small ponds rather than working together. Noble in some ways, petty in others. To be jealous (if that is the right word) of Linux, or upset that it's grabbing the lion's share of developer attention, seems more like they are getting what they asked for.
I have a hard time visualizing any of the BSDs being happy at all the changes made in the Linux universe. I rather think they'd turn up their noses and reject the impurities.
I have no personal experience with developers in any camp. But the squabbles from the various BSDs all seemed far more petty and even snobbish, so again, they seem to have what they wanted, and if they don't want it now, maybe it's not too late to be more open to each other. The first step would seem to be unifying the BSD variants, but I don't imagine that's a particularly easy job, either politically or code-wise.
Or maybe the BSD folks are happy in their small camps. It's their code, their choice.