If you have a need now, build now.
If you wait, you will wait forever for the next best thing.
With your budget, you can build around a 3570K and plan on passing up haswell. It should be good for 4 years.
Haswell will bring perhaps a 10-15% performance increase at current prices. It is unknown if the OC capabilities will be significantly better. But most games are not cpu bound, or at least not limited by a 3570K with a mild overclock.
As to the graphics card, the situation is similar. The next round of cards will be evolutionary in nature. The top end cards will offer more top end performance and command an appropriately premium price. The midrange cards will have to compete with current cards on a price/performance basis.
My take is to build now.
Plan on a mid-life graphics update.