...I figure they'll always be considered a 'Periphery' realm, given they're outside that magic 500-ly line that defines the 'Inner Sphere' and 'Periphery'.
I don't think they'll ever formally join into a single nation, after what happened after the F-C debacle, either. Allied Realms, sure. But besides the distance from Terra, technology was the real divider.
I haven't read much about the DA, but I get the feeling that even after seeing Primitive mechs could defend Hesian (?) from the Wobblies and bulk up the armies of the IS, the example was lost on the canon Periphery realms. Too bad, it could have been interesting, seeing the highest tech around Terra with fewer and fewer high tech weapons the further away from Terra you got. That way the whole of the rulebook might have been used in the canon setting.