The firmware upgrade to the A900 and A850 is likely to be announced by 2nd December. The new manuals have been leaked in Hong Kong according to 'Sony Rumours'. The latter show a screen shot of the manual listings.
The improvements are reported to be:
* Release shutter without lens (same as A580
* EV compensation upgrade from +3/-3 to +5/-5 HDR enhance from +2/-2 EV to +3/-3 EV (same as A580 upgrade)
* Improved AF speed and accuracy.
All seem very sensible to me!