While we're expecting the Haswell chips to launch soon, we haven't seen Ivy Bridge-E chips hit the market yet (the current Core i7 Extreme chips on the market are based on the Sandy Bridge architecture). Before we see Haswell launch though, we are expecting the high-end Ivy Bridge-E chips to round out the generation sometime in the second half of 2013.
X-bit Labs has made a table that gives us a good overview of Intel's plans for the -E lineup of products. Looking at the numbers, we can see a clear difference between the chips. While the cache and TDP are quite similar, the clock frequencies have taken a little jump, as well as the memory controller, which jumped from supporting 1600 MHz memory to 1866 MHz memory. The performance jump appears to be minimal, and unsurprisingly so. Ivy Bridge didn't improve much on performance over Sandy Bridge. Note, though, that the specifications listed are still unofficial. What we do know is that buyers will be able to drop the chips right into existing LGA2011 motherboards.
Based on the numbers given we see the successor to the i7-3820K as the i7-4820K, the i7-3930K is succeeded by the i7-4930K. Similarly, the i7-3960K is bettered by the i7-4960K. What we don't see is a successor to the i7-3970X; however, we could assume that down the line Intel might introduce an i7-4970X to top everything off. This is not shown on Intel's roadmap below, though.