Not true. LGA 1155 parts, i.e. the ones for iMacs have been out since January 5th. High-end desktop and server parts for LGA 1356 and LGA 2011 sockets will be released in Q4 2011 but it's unlikely that Apple would use those in iMacs.
Just be patient please ... it's only 2 days for the new MBP, and waiting usually better. This way iMac specs can be enhanced further
People tend to buy MacBook rather than iMac or even MacPro. That's why MacBook get a headstart. But you see, main treat always come last, and so does iMac