Certainly if you simply want a gaming machine that gives the best performance per dollar, the I5-3570K is the way to go, no doubt. Of course you will want to overclock it.
I, however, am intrigued with the Haswell. It will be about 5 to 10% faster, clock to clock, than the Ivy Bridge. That alone is nothing to sneeze at. Just think, you'd have to overclock a Ivy Bridge to 5GHz, which cannot be done without liquid nitrogen, to equal a Haswell at 4.5GHz, a value, that at least with Ivy Bridge, is reachable with a good air cooler.
Beyond that, the Haswell has many architecture improvements that will save power, which equals faster clock frequencies. Look for the Haswell to be more overclockable than the Ivy Bridge. Also, many of the improvements have to do with making it easier and faster for multi-core programming. Look for more multi-core games and other programs. It seems that with new drivers, the Haswell can be many times faster with some programs/games as it will ease and simplify the transition to multi-core programs. The 1150 motherboards will have greater functionality and will be more future proof than the 1155 boards. For the wait of only three months, I'm waiting.
I note that you will be doing some engineering programs. I am a chip designer, and multi-core programs run much faster. I'd say you should wait too. Of course this depends on your immediate needs.
I think I just may buy the I7-4770K, for those eight threads will most likely be used in the following year or two by games and engineering programs alike.