The old post of December 7, 2011 on Bethesda Blog stated:

"We’re also planning on rolling out support for 4-Gigabyte Tuning (Large Address Aware) next week for our PC users. Stay tuned!"

...but the latest update stated:

"For PC players, the Large Address Aware update is currently in testing. More to come soon."

Which strikes me as weird...because...well...you could make a file compatible with LAA just by editing the exe, which takes less than 2 minutes...so I was wondering:

Is this going to be a 64-bit compatible patched exe?

I think its just a LAA. I would love it if Bethesda surprises us with a 64-bit exe (though I highly doubt Bethesda would make a 64-bit exe).

EDIT: They probably ran into problems.

Adding the tag isnt as safe as one would assume, but its better than crashing so often.