Sony Ericsson seems to have started pushing Android 2.3.4 update for Xperia Play. The exact regional availability of this update is still not clear (apart from Nordic countries), but you can always check on your PC companion software for the update. OTA roll-out is expected to take some time.
Full change-log has not been officially announced, but according to several XDA members, this update will enable video recording at 720p resolution with continuous auto-focus on your Xperia Play. Other changes include Swype keyboard, new screen on/off animation, Facebook inside Xperia, Gtalk with video and automatic brightness off/on.