According to our sources (Thanks!) the new Sony A850/A900 firmware will be announced on December 2th. The main improvement will be the auto focus speed and performance. We have no reliable info about a possible image quality improvement.
Stay tuned on SonyAlphaRumors!
P.S.: In US you have tons of Instante Rebates on Sony cameras and lenses. I couldn’t find any deal in Europe (I am one of those guys waiting for some nice european A850 deal).