Intel's server parts are expensive, but they are worth it if you're running a mission critical application. Currently, the server chips are based off of the Sandy Bridge microarchitecture and it looks as though it will be staying that way for a while longer. Ivy Bridge-based server parts aren't due out until 2013, according to the latest roadmap.
The upcoming server platforms are called Brickland and Grantley and which one you use will be dependent on what sort of applications and processing power you are looking to utilize. Brickland will be used for mission critical applications and is set to support three generations of CPUs all the way through to Broadwell in 2015.
Grantley will be for efficient performance and won't debut until after the Ivy Bridge generation. The first chip that Grantley will support is the 22nm Haswell server variant. They will also be introducing a new storage controller which will bring performance and feature improvements. We should learn more as of Intel's upcoming meeting in San Francisco.