I think it's a crap shoot joining a newly forming community. You might ride a promotion and billet wave through your career and retire, or you might be stuck in a spot where the powers that be really don't know what to do with you, so you either find a new job or simply go away.
From some of the briefings that I have gotten, the MQ-25 is a cool airplane with some capabilities that, assuming the Navy will use them, can make it a viable weapons system and value added (beyond a recovery tanker) for the CSG.
If the RPA/UAS community is what you want to do career-wise, I'd recommend to go either to the USAF or the ANG. It's a well established community with multiple TMS that supports a lot of different types of units- to include the CSG.