They are raised by Mawsworn now, so I guess that does not include giving them free will.
Well, when void elves were formed, san'layn were not part of Umbric's group, so I don't they should get that option. On the other hand, I wouldn't mind, but in that case, prepare for rivers of tears from blood elf community, which requests san'layn for blood elves. Most blood elf fans are not really happy how little customizations they get and complain all the time void elves got their skin tones, so void elves getting san'layn skins while blood elves don't will make a lot of people upset. I don't think it'd be fair to blood elves either.
To be honest, best scenario would be san'layn allied race on the Horde to show they are their own independent group with selected classes fitting to them. I'm not sure if we ever get another allied race though.