We havent heard anything in a couple months though.
An upclock and/or increase to say 12GB RAM is possible (and dirt cheap, because DDR3 is).
Southern Islands 10-12 CU chips in the wild are typically clocked at 1ghz at retail (such as 7770 and 7790), with overclocks pressing beyond that (
this 7770 is clocked at 1100mhz.) So even a 20% overclock to 960 mhz seems reasonable as it's still less than stock retail 7770/7790.
MS would feel the need to respond to "8GB GDDR5!" hoopla (which remember, didn't exist prior to Sony's event). They also could be getting behind the scenes blowback from devs who feel Durango isn't keeping up. Which is really who they have to answer to. This wouldn't be happening in a vacuum or without reasons to do so.
The baseline for next gen will be Durango/PS4/PC. Durango cant start too lag too much, it just cant. They all have to be targeted with roughly the same assets or it doesn't work.
If I had to guess at anything, I would start at 12Gb DDR3. Like I say, it would be cheap. 16GB would be overkill. 12GB arguably would, but it would allow them to reserve 3GB while still entirely matching or exceeding PS4 with 9GB free at a a minimum. Even if you couldn't efficiently use it all for gfx, it could help with loading times etc, worst case. It would give them something to placate fans and developers alike in the spec wars. It would give them their own "ooh ahh" spec to announce at the event, etc.