Apple could be waiting to time the launch of the new iMacs with the launch of Mac OS X Snow Leopard operating system, which is expected to ship sometime around June. Snow Leopard is expected to improve the way Mac OS X handles multicore processing and graphics processing. Apple is debating whether to use Intel's dual-core processors or newer quad-core processors in the new iMacs. The dilemma is performance versus power consumption, as well as concerns that using quad-core chips in the iMac could steal business from the Mac Pro, currently the only system in Apple's lineup that uses quad-core processors.

Source:→ CNet