The extreme4 board is better than the extreme3 for OCing. It has more power phases which will deliver better power to the CPU when OCing. I wouldn't wait for it.
This post is a over a month old, he's already purchased the extreme 4.
Also both the extreme3 and extreme4 are 8+4 phase, please don't spread misinformation. http://www.asrock.com/MB/overview.asp?Model=Z68%20Extreme3%20Gen3http://www.asrock.com/mb/overview.asp?Model=Z68%20Extreme4%20Gen3