Pretty much what Graet said. Don't go and buy new GPU's unless you intend to use them(gaming) beyond the point when GPU is profitable, or you're able to sell them when GPU becomes unprofitable(costs the average person more in electricity to run the card than it pays out.)

Some factors to consider:  How much do you pay for electricity? Will you be able to sell the GPU for enough to make it worth it while mining with them is still viable?

There is alot of skepticism surrounding the production and utilization of ASIC devices. It's all been a gamble since the $30 bubble of June '11 and subsequent decline; the new gamble is investing in ASIC hardware. Alot of people have put their bets in ASIC development, but even more people have said it's BS.

If I were you, I'd try and pick up GPU's 2nd hand for cheap, and try to re-sell them to gamers in late December for pretty much what you paid for them. That way your only real investment is purchasing the electricity used to power the card(s) for a few months and stack some coins to hold onto. I'm becoming less skeptical of ASIC devices myself as there are now 3 different vendors offering pre-orders, not just butterfly labs. Of course it could just be "hey, that guy's doing a long con, I should do one too"...