I think you have relationships with people the same way you would with anyone else. Just because they identify as submissives doesn't mean they will be submissive to HIM. And even if they wanted to, I doubt he would let them just because they asked nicely. "You are not entitled to a relationship with the person of your choosing" and all that.
As far as him wanting that again someday, I'll cross that bridge when and if I come to it. Until then, I trust that what he wants right now isn't that, and I can work with what he does want, and what I want, to make a good, working set of relationships. (Including the ones I might want with other people. Because our play partner is cute.
I guess you could say that I trust him more than I trust my gut, because I'm in the middle of a depressive spiral right now, and my gut is telling me all sorts of things that aren't true (like the fact that the bathroom razor looks attractive, which is obviously a fallacy, case in point). Whereas he tells me things that are true, and has proven himself worthy of my trust in the past.