Personally, I would do it sooner than later - if I could get some published specs to help me with the purchase of a new, dedicated slave machine before the new software ships.
I want to do a Mac Pro for VE Pro. I have a Mac Pro for VE3 but am running it in Boot Camp/Vista 64. It would be nice to know how much RAM I could access if I chose to go for the Mac OS. I'm trying to avoid using a Windows OS for Play.
Currently Kontakt is covered adequately entirely within my main Mac Pro DAW by using some within Logic and one rather large library in Plogue Bidule.
I do expect VSL to do a pretty good job on the first iteration. Perfect? That will be difficult because the audience they're playing to is large and diversified.