Broadcom has announced a single-chip 802.11ac device.
The BCM43460 is a switchable dual-band (2.4/5 GHz) IEEE 802.11ac draft- compliant SoC incorporating MAC, PHY and radio. Its 3 X 3 (three transmit, three receive) MIMO design supports link rates up to 1.3 Gbps on the 5 GHz band for 802.11ac operation.
The BCM43460 is sampling now with production volume slated for the "second half of 2012".