I didnt suspect this thread would get this many comments anyways after reading over everyones comments i believe a revision in the design will not occur this year for these reasons:
1. Steve Jobs will present the Imac at WWDC
2. Change comes with major revision of OSX blu ray support more hotter components
3. looking at a timeline i found on the web apple seems to keep the same design for about 4 years sightly modifying its apperance making it thinner
I agree about a major change in design...but I do expect an update to the existing line on either July 13th or August 17th. Probably a jump in GPU and/or processor speed and more memory.