If you need a new system now, buy the best system you can afford now. If you don't need it now, then wait.
The refurbished 2.26 mbp for $999 at the apple store is a pretty decent price. If you can buy online and wait a few days, I'd choose this option over buying a new white macbook at best buy for the same price.
Do you not have a computer now? Or does the one you already have not do what you need (not want) it to do? Then you probably need a new system now.
If you already have a computer, and it does what is necessary for school and/or work, then you don't need a new computer. You simply want one, or are lusting after whatever tasty new features apple has included with the latest model.
If you're using your computer to make a living, you should know what your time is worth. Realistically estimate how much of a performance gain a new system will give you and see if it will at least pay for itself in a year or two. If it won't, then stick with your current one. My fiancee's uncle is a graphics designer in my state's largest newspaper, and they're still using g5 powermacs with CS2 to do their advertisements. Even with craigslist, they've still got enough money to buy mac pros with cs4 if they thought for a minute it would result in a performance and profitability gain.
If you're not using your computer to make a living, keep using it until it breaks down (hopefully under applecare) or no longer does what you need it to do. In either of the above two cases, you can often goose some extra life/useful performance out of an older system by maxing out the ram and adding a larger, faster hard drive for a lot less than the cost of a new system. The upgrades may also help you sell your older system if you are so inclined.
If apple introduces a new system in a few weeks or months, a current system won't magically stop working or no longer do what it is doing today. Even if apple releases a quad core mbp with 10.6, I dare say that it will still take programmers a while to optimize their apps to take advantage of the new capabilities.
Sorry for the long winded rant, but it gets tiresome at times to read all the 'buy now or wait' and 'should i sell my month old mbp and buy a ...." threads.