Politico interviewed Scott Walker by phone on Monday. For all we know Mitt Romney will be seeking re-election in 2016 and it's a moot point. But this piece paints a picture of Walker as someone who now welcomes a national role. And he's right, you don't get political capital by sitting on what you've already earned.
As for the line about democrats still hoping the John Doe probe will "ensare Walker himself." It's a two year fishing expedition that may never end. And Scott Walker is now more the standard bearer of the Republican party than is Mitt Romney. The GOP powers that be don't seem to worried.