I don't think that weight mapping would have to make old models obsolete. After all, Carrara converts Poser figures to it's weight mapped rigging, conforming clothes and all. If Poser's rigging were updated, there is every possibility that it could do the same.

On the other hand, I'm not so sure that we will see weight mapping this time around - a lot of time and fuss has been made about the new rigging method for the G2 figures that uses magnets coded in the cr2 instead of JCMs. Just my feeling anyway.