OP is based on a false premise. As Bernie himself stresses repeatedly, his campaign is not about Bernie, it’s about his ideas. Bernie is probably happy to serve out another term. He’s approaching retirement age and is himself surprised that he almost came in first in Iowa.
The real significance of Berney’s electoral success is how it broadens the range of permitted discourse and informs decision-makers of Americans’ appetite for change.
For example, after Michelle Bachmann …
… won the 2013 Straw Poll, the GOP learned to adapt to appeal to voters who were batshit-insane. Similarly, if Bernie wins the N.H. Primary, the Democratic Party may need to adapt to voters who put the future of democracy and the welfare of common American citizens ahead of the interests of the super-rich.