Hey, Why Not!!! Her top choices right now are senators in states with Republican governors who would (no doubt) choose Republican replacements. In Biden, Hillary would have a running mate who is popular, a strong debater, and (most importantly) capable of being President should the need arise. If she could talk Biden into hanging around for another four (or eight) years, I don't see a downside. He's already proven himself to be a great VP.
http://www.nydailynews.com/news/election/hillary-stop-biden-time-give-joe-vp-nod-article-1.2668495