You definitely want to wait for the Haswell. There are many factors pointing that they may be a huge step forward like Sandy Bridge was. Not to mention that it uses a new motherboard, the Z87, making the other Z77's obsolete. Plus its pricing seems to be the same as the Ivy Bridge. Here are the advantages:
Again, about 5% to 10% faster per clock cycle. May not seem like much, but it does mean a Haswell overclocked to 4.5GHz will be as fast as a Ivy Bridge overclocked to 5GHz, not bad.
They seem to be using a better heat solution this time around. This is huge, look for much better overclocking.
Architecture far better for multicores-threads. Look for more and more software support for multi-threads. Remember, using extra threads...