When it dies go mine a newer coin, there are plenty of altcoins to mine with a GPU, although not as profitable.
Watching whattomine.com over the past couple days is making me think this is probably unsustainable. Profit is razor thin already.
People are buying more and more GPU's just to mine, something has got to give. It might get to a point where miningprofits will be negative in 6 to 12 months, but people won't stop mining in the hope of a massive pump on the exchanges. Who knows what the future will be, it might get ugly.