Will work in old boards but…
We have managed to get some details on Ivy Bridge's ability to work across the platform or desktop platforms and feature cross compatibility, as Intel likes to call it.
As you can imagine the best combination is Ivy Bridge CPU and Panther Point, a solution that will give you all the features and if you use that CPU with Cougar point or Sandy Bridge on Panther Point, you will miss some things. Ivy Bridge and Panther point will give you IA Performance benefit from new 22nm process, Integrated USB 3.0, DirectX 11 graphics with three independent displays, Intel small biz advantage, 2012 vPro / stabile image platform program (SIPP), Intel firmware recovery (IFR) and both Pentium and core version of Ivy bridge will give you 2012 Intel standard manageability (ISM).
In case you go for Ivy Bridge and Cougar point you get the 22nm IA performance from the new CPU and DirectX 11 support from a CPU but you miss out on all the other listed features.
The third combination with Sandy Bridge and Panther Point will miss the IA performance from the new CPU as well as DX11, 3 display but it will give you an USB 3.0 support 2012 Intel standard manageability (ISM) with Pentium processor and Intel firmware recovery (IFR) support.
The last possibly combination that you have today that includes Sandy Bridge CPU and Cougar point chipset will miss out on all the features, apart from 2012 Intel standard manageability (ISM).
The bottom line is that Ivy Bridge works in Cougar point chipset and Sandy Bridge will work in Panther point next gen chipset.