Even if he does, he certainly isn't going to get to be President by just doing nothing for the next 6-10 years.
The 'Senators Can't Get Elected' crap is a myth. The last 3 that have tried have been total yutzes, didn't have anything to do with being a Senator IMHO.
I would agree that being a Senator automatically doesn't mean one is disqualified, but for some reason, in the last 40 years or so, it seems to have become a higher hill to climb. The reason I would surmise, is that as a Senator, you have so many votes you cast (procedural or otherwise) that can give the opposition a mountain of evidence that can be used against you in a very negative light. Merely the fact that Bob Dole, for instance, was even in Congress serving in the leadership opposite Newt was enough to mortally wound his candidacy (even though it need not have). You end up carrying the burden of every other member of Congress with your party label. As a Governor, you tend to be judged more as an individual.