You need to understand the test procedures. These aren't minimums - they're averages. And the 2007 tests are not realistic for most drivers. e.g. they don't use the A/C, the speed is much lower than normal, etc. For 2008 the EPA is changing the tests to be more realistic. Instead of 17-24 on the AWD it will not be 16-22. If you drive worse than the EPA tests you'll get less than that. You could also get more.
Figure out what you get now relative to the EPA rating on your current vehicle and that will give you an idea of whether you'll be at, below or above the EPA ratings (2007) in the new vehicle.
Lots of good info including a comparison of 2007 and 2008 EPA ratings: http://www.fueleconomy.gov