I can tell you right now, from experience, that the biggest roadblocks to renewable energy developments is the NIMBY, BANANA, and NOPE contigency, especially with respect to transmission. And it is much easier for local opposition and advocacy groups to build and organize these days with the Internet and social networking tools.
You forgot NOTE. 
-XT
Probably basically the same as NOPE.
Yeah, NOTE is a subset of NOPE. NOPE is actually completely insane, while the rest are just stupid.
-XT
OK, NIMBY = “Not in my backyard”… What are the others?
NOTE = Not over there either
NOPE = Not on planet earth
Personally I think there is a lot more untapped wind potential than you admit- I would say as of now American Wind is ‘mostly untapped’, as opposed to your view of ‘some untapped potential’. North Dakota, Texas, Nebraska… none of these places is anywhere close to saturation with wind turbines. You might consider much of the North Dakota plains to be ‘second tier’ compared to some super-windy location, but since there are miles and miles upon miles of it, it amounts to a ton of potential that can very realistically be developed.
I don’t have an estimate of what total % of energy needs could be met with wind… sounds like an interesting debate in itself.
Decades? Hundreds of billions? Oil math is on this scale too. What else do you got? Nuclear? I appreciate the massive output nuclear power provides, but I am leery of any accounting of its costs, considering the 25,000+ year ‘tail’.
BANANA = Build Absolutely Nothing Anywhere Near Anyone