Yes, the same work will soon be worth half as much. At Bitcoin's current value, you will lose money mining with a GPU unless you live very close to a power station and have cheap/free electricity. However, don't let that discourage you. If you want to try mining, by all means, go for it, but don't invest a bunch of money into GPU-based mining equipment at this stage in the game. That 72GH/s device you were looking at has been delayed for production until January 2013 at the earliest, so it's possible that you can make some coins before then. Once ASIC devices hit the market, combined with block reward halving, mining with anything but an ASIC will make very little sense unless BTC value goes up.