User blog comment:Blood Reaper/Skyrim Update Coming soon/@comment-3991220-20111118233509/@comment-2041582-20111119173258

(to the anon above) Well, yes, but they spent half of the time you described working on Fallout 3, so 2-3 years on Skyrim is more accurate. But even half of that time is usually spent brainstorming and working on the new engine (which is obviously just the heavily modified Gamebryo Engine from Oblivion, which itself, even is the upgraded engine from Morrowind), so I'd say they spent about 1.5 years working on the actual game. That's about the time they release a teaser trailer to go with it an notify the fans that they're officially working on it.