Obama's feckless rule has caused Dem wipeouts in both off-year elections, and allowed the GOP to retain the Senate this year against all odds. In 2018 it will be the Dems' turn to shiver in their boots at the odds of avoiding more Senate losses.
Where's the young blood? The Dems don't need Joe Biden to run for President in four years, they need to develop new faces, including ones that are less strident ideologically. Folks like, say, Corey Booker.