Digitimes is claiming that Apple is ramping up production of "Retina" display iMacs for an October launch. They report:

"Apple's supply chain reportedly will start supplying components for the mass production of Apple's upcoming new iMac all-in-one PC in July with the device's official launch possibly around October, according to sources from upstream supply chain."

Digitmes has a long history of publishing rumors that don;t come true though so don't hold your breath !