I think the price for GPUC should remain fairly stable, once the store opens up and we have some idea about how many GPUC it will cost to get one GPU. I think the GPUC should be in some way self-correcting because anyone who buys GPUC to get a GPU is going to check it against the value of BTC and their national currency. The volatility might be more connected to BTC volatility than manipulation of the GPUC market.
The only way I see extreme volatility is if there's a lot of dumping all at once or if the GPUC store is the only place where you can find, for example, 290x GPUs.
Honestly, if you believe anyone mines that coin to buy GPUs you are just naive.
Who mines it is planning to dump it as soon as the price is profitable enough. Some of the miners bet on people that are expected buy this coin to get GPUs, but really look at it: You get GPUs quicker and cheaper on big markets than here - especially outside of north america. As said before, the whole model is a flaw, and if the creators are aware of the flaw instead of being totally naive, a scam.
You are forgetting one important factor: Good GPUs are freaking HARD to find. And if you find them they are extremely expensive. You might have some inside information or some contact that you can use to get GPUs at a reasonable price, but the average joe doesn't. This gives us one more method to obtain the GPUs we want.