MIR 3D will replace MIR Pro, that's for sure. I don't know about plans to integrate MIRx with Synchron Player (... which doesn't mean that it won't happen at all). In any case, it is quite obvious that the idea of "burnt-in" spatial information, on which VSL's Synchron series is based, requires different workflows and different tools.
Best,
/Dietz - Vienna Symphonic Library