I can definitely see the inevitable movement of GPU number crunching power shifting from Litecoin to Primecoin market as soon the a GPU miner becomes available publically. It's just a natural order of economical distribution. Litecoin rose int he midst of Bitcoin's GPU mining fall, and so will Primecoin do to Litecoin. The only thing we've yet to witness is an Asic Scrypt miner to make that transition complete.

And since there will be many more people involved when GPU mining is possible, the demand will naturally rise due to more people involved with the coin. Just like Bitcoin, its price is only as high the people holding are willing to sell at.

Prices can be crushed down by a few hoarders and dumpers, but to rise consistently, it needs adoption rate in quantity, and that's what will happen when GPU mining comes out.