It’s good for Barack Obama, too. To the extent that second-term presidents have problems, it’s probably in large part a function of presidents thinking past the next election and toward “legacy.” That’s a terrible idea for presidents; it removes them from the clues to good policy that are basic to the electoral system. Anything that can realign the White House with the electoral system is a good thing, and so a vice president running to succeed the term-limited incumbent has got to be better than nothing. And that’s not just good for Obama; it’s good for the nation for the president to be governed by electoral incentives instead of whatever he happens to think would look good in his presidential library.
Both of those benefits should happen even if Biden eventually decides that a full national campaign isn’t a good idea; indeed, they’re good enough consequences that Biden should probably fake it even if he knows he’s going to back off sometime in 2015.