Honestly, I don't think they would have chosen Skyrim for the provence of TES V. It would have been something like Black Marsh, Elsweyr or Summerset Isles. I think the Fallout stuff helped them decide the location based off of the landscape of Fallout.
Yeah they would have because there was speculation and even a website somewhere before Fallout 3 with Unofficial leaked info that they already had the Province of Skyrim planned. Maybe BGS would have built a new engine if they weren't pi**ing around with the Fallout series between TES games and had time to iron out the problems. I see alot of people post the crap that BGS had 6 years to make Skyrim which is DEAD WRONG. They worked on FO3 between there. Which IMHO didn't give them the proper time they ususally had to work on TES and fix the issues.
I have said it before about the way BGS has been working the last 6 ot 7 years now. Too many hands in the cookie jar and too many cooks in the kitchen. All Zenimax wants is for BGS to make them profit at any cost. Simple bottomline of Business.