LGA 2011 mobo compatible with ivy bridge?

Yep, all current chipset LGA 1155 (SB/IB)and LGA 2011 (SB-E/IB-E) will support their Ivy Bridge counterparts IB and IB-E respectively. The only limitation is the OEM MOBO's providing the appropriate 22nm CPU BIOS. As far as 'faster' LGA 1155 IB vs LGA 2011 SB, I don't even want to venture a 'guess'; last year I was confident that the SB-E would swamp the SB but I was wrong. The SB-E is faster but it's closely shadowed by the SB.

I do 'expect' the 22nm to be more efficient and thereby high OC per temps, but at what Tjmax?!

IMO the reasons to get LGA 2011 are that you want 3/4-WAY, Apps used benefit from 6/12 core/thread, need 32GB or more RAM, and/or simply want the 'best'. To this day I'm still aggravated Intel elected to disable cores 7 and 8 (8/16) -- they're there!!!

That said, if the plan is to get an IB-E then sure the i7-3820 4/8. Keep in mind you're limited to x43 CPU Multiple and I'm not certain if you can BCLK/Strap OC (e.g. 133MHz * 43 = 5.7GHz maybe on LN2 <or> 100MHz * 43 = 4.3GHz).

Generally, I'm personally not a fan of buying 'old chassis' for 'new engine' in other words there will be some added performance with newer chipsets and in some likelihood also better more finely tuned MOBO's tailored to the IB-E.

The LGA 1155 IB i7-3770K comes out of the box with 3.5GHz/3.9GHz. I've been learned not to assume anything until it's in hand, tested, and thereby proven. Also, if you decide on the i7-3930K be aware there was a bug with Vt-d (C1 / C2), which is the reason for the SB-E delays and inventory problems, as of now all new SB-E have this fixed.

You cannot get stuck in the tomorrow there will be syndrome too much unless there's an immediate need. I 'get' everyone wants the next gen stuff, but if upgrading you need to consider your options.

Example - my situation I have both LGA 1366 and LGA 2011 and there's not an OMG urge to ditch my i7-980X gaming rig. The only compulsion I have is to replace my 3-WAY GPUs with the newer GTX 600's due out soon. PCIe 2.x vs PCIe 3.x on today's GPUs offer little to no advantages, in a few years probably it will make a difference. I'm hitting a few games where I'm crippled by vRAM bottleneck - not by a CPU bottleneck. I can justify the GPU's but not the (MOBO, MOBO block, RAM & CPU) or $2K+ for just 2~4FPS. My Gaming rig replacement will be either the IB-E or more than likely the Intel 'Haswell' unless my LGA 1366 dies beforehand.

Unless your needs are as stated per my prior post, IMO if possible cool your jets and wait just a smidgen longer for the LGA 1155/IB with a Z-series Panther Point chipset MOBO release -- then give it 2-3 weeks for the early adopter head banging to be sorted-out and then buy if there's no bugs.

Yep, you've got the right idea!

Good Luck!