You can do this right now, between Maya/Max/Soft and Mudbox, its only the single step interop isn't quite as tight as it is with Maya. But essentially its FBX underneath.
As for GoZ, that's really down to Pixologic, sure there's an SDK like there is with FBX, but as someone has said, why would Autodesk support that when, imo, we have a perfectly viable and production proven alternative to zBrush with Mudbox and also a tighter interop and data exchange then GoZ.
True, but Mudbox is just playing catch up with ZBrush at this point. Capabilities of ZBrush far outweight those in Mudbox. I do like the interoperability between Mudbox and Softimage (except if you send back to XSI it doesn't update the mesh you sent out ie: A rigged mesh's geo).
The interop Hub needs an SDK so we can help build pipeline tools to other apps. It'd be the considerate thing to do from AD as we're not just talking about other 3D apps that need to interact with the AD software but also our own custom apps and pipeline tools.
In some areas yes, others no. It's only on the modelling that zBrush has the jump on Mudbox, but Mudbox isn't that
far behind. I think many people forget how good Mudbox is, but many are just more familiar with zBrush and I can see why.
The Autodesk interop is obviously built with Autodesk apps in mind and there is some SDK capability for it, but its all around FBX. I have seen other studios build similar interop work flows with their own tools and formats, or they've taken the FBX SDK itself and done something else.
As for GoZ, well honestly I think the ball lays in Pixologics court and I'm surprised they don't do something. I think they're missing a few tricks, some of the recent previews and features do look very good indeed, but personally people seem to be easily sucked in. What would zBrush users rather have - hair or a much improved GoZ interop with their 3D package?