So, they're the only non-hostile Mogu in the game... BUT Ra-den went and kicked the bucket after getting corrupted, so what do you all figure will happen to The Rajani... and the rest of the Mogu?
Personally I'm still hoping the Horde manages to wrangle some of them.
They'd be a potential buddy race to the Forsaken. Use anima/blood magic same as the Belfs and Bleeding Hollow Mag'har. And it'd give them a chance to mend fences with the Zandalari and Pandaren (Huojin). That'd be an interesting story angle, how to reconcile with folks you used to abuse... and then that could dovetail well with Horde relations with the Alliance.
Mechanically it'd also give access to the Draenei-male skeleton and whatever skeleton the female mogu use (Female draenei? Female worgen?)
Mogu use of spirit magic could also have them show up later in Shadowlands, or in the next expansion pretty easily.