Apple has dropped the 20in PowerPC-based iMac G5 from its online stores in the UK, Europe and Japan. The product will likely soon not be available in the US as well. Focus is now shifted to the Intel-based MacBook and Mac Pro.
Speculation points to a 1 April - the date of Apple's 30th birthday - for a MacBook announcement, but the high-end desktop isn't expected to be replaced until Intel ships its 64-bit 'Conroe' processor in Q3.