I think Tyger Purr has hit it on the head very clearly.

Poser Pro is 7 Plus additional features for advanced users.

Poser 8... well we have no idea at ALL when or even IF there will be a poser 8, so that would be pure speculation.

I'd think Poser 8 would a have enhancements to Poser 7, and a "Poser 8 Pro" would include it's enhancements, and the additional ones in "Poser Pro" (7)

Way too many people take way too many things way too seriously.