If you are content with the current performance, then just wait for benchmarks. Steamroller should provide better performance than PileDriver, but I am not quite convinced yet that it can be equal to Ivy Bridge. Equal to Haswell? I really don't think so.
If your cash is burning a hole in your pocket, then simply upgrade now. Some people recommend buying the i5-3570k instead of the i5-4670k because Haswell in general does not overclock as well as Ivy Bridge.
Depending on which set of performance comparison reviews, it seems Haswell's performance increase compared to Ivy Bridge ranges between 6% to 10%. I go with the more conservative 6%. Therefore, an i5-4670k OC'ed to 4.4GHz is equal to an i5-3570k OC'ed to 4.66GHz. A 10% performance increase would mean the Haswell i5 would be equal the i5-3570k OCed to 4.84GHz.
With regards to Ivy Bridge-E, I'm not exactly sure when they will be released. The prices was recently released though. I believe the price ranges between around $400 for the 4 core IB-E CPU and up to around $1,100 for the most powerful 6 core IB-E CPU. I think the least expensive 6 core IB-E comes in at around $650.
To me, I don't see the point of buying the 4 core IB-E CPU. I would only consider buying the 6 core IB-E CPUs. The question is whether I am willing to pay the price for the 6 core IB-E is a different question.