WI, PA and MI aren't going to be republican.
I would not bet on that. 25 years ago people thought Virginia was solidly Republican, that it would never go Democratic.
I mean, I know people believe that because Obama carried these states by a smaller margin in 2012 than in 2008. The fact is that Obama really overperformed in WI, MI and PA in 2008. If you look at the results in 2004,2000, 1996, it is relatively similar than in 2012.
Yes, he over performed in the Midwest in general in 2008 (especially Illinois and Indiana). These have been Lean D states for a while, to surely suggest they won't change politically though is risky.