Everything else aside, Terran and D'Hara have pretty much zero reason to continue fighting if Barca defects. I mean, D'Hara is intact, Terran is intact, and most of the rhetoric was over reclaiming Barcan regions, yet Twainwood defected. OOC, I simply don't see this lasting much longer.
Rynn would rather be fighting Lurians anyway. That's the cool thing to do.
I can very much imagine this happening, particularly in D'Hara. Of course Constantine will vehemently oppose it if it does but most D'Haran's are fundamentally pragmatic.