Intel isn't really in a rush to release its new high-end processors due to lack of competition, in the fourth quarter of the year we can expect the Core i7-3970K, the final Sandy Bridge-E part, and even though Haswell is expected in Q2 2013, the Ivy Bridge-E processors won't arrive until Q3 2013.
The upcoming "Sandy Bridge-E" based Core i7-3970K will be a six-core model with 3.5GHz stock clockspeed and 4GHz Turbo. For the Core i7-4900 series "Ivy Bridge-E" you'll have to wait roughly one more year, it uses the 22nm process and 3rd-gen HKMG technology, and features a quad-channel memory controller with DDR3-1866 support.
Interestingly, Ivy Bridge-E sticks with the X79 chipset and this means we'll see two more X79 motherboard refreshes. The first refresh is scheduled to appear with the Core i7-3970K, from limited number of vendors, and a second X79 refresh is scheduled for Computex Taipei 2013, with the arrival of the Core i7-4900 series processors anticipated for September/October 2013.