I'm not sure when Ivy Bridge mobile CPUs will be release, but it is usually after the desktop CPUs will be released. Since desktop Ivy Bridge is expected to released in March 2012, the mobile CPUs may be either April or May 2012.
Some sites estimate that Ivy Bridge's CPU core should be up to 20% faster than Sandy Bridge's CPU core. The expected big improvement is in the graphics core which is estimated to be about 50% - 60% more powerful than the Intel HD 3000 graphics core. That sounds impressive, but that would only be a little faster than the desktop Radeon HD 5550 graphic card.