Well, I have to say this. I wish they fulfill 60 months cycle this time. Their tech needs lots of improvement. Looking at Fallout's development time, when applied to TES, guarantees 60 months dev time. In my opinion. (Although, this time I have to think that they were working on the new project full-scale, or half-scale during Fallout 3's devolopment. I pretty much think they don't use Gamebryo tech as it was and was working on the engine full time before FO3. They simply decided to use old tech one more time for FO3 and focused all the dev time to new project. This time they really tried to systematize things, which is why the actual content development is taking less time.)
Let's say they announce it soon and not follow FO3 but Morrowind or Oblivion.
Then we can be 18 months away.
If we take Morrowind, then 26 months.
I agree with an November announcement so.
March 2012
or
A late 2012 or 2013 release.
If it is the shortest than, let's say 12 months.
December 2011
If it is shorter than that, where is it gonna be shown in 2010-2011 then? They can make a surprise announcement like DNF on an event.
Maybe they release a DEMO this time too.