Just another speculation... Do we think Disney will sell individual location pieces such as the cars piston cup, for those who are interested in cars play set but don't want Lightning an Holley an just want mater? Or will the only solution be to borrow your friends piston cup piece?
borrowing won't work to keep something permanently. unlike skylanders adventure packs the world is only available while the play piece is on the Infinity Base.
personally at this time i doubt that play set pieces will be sold separately especially early in the product life cycle.