I doubt Bernie would run this year- but he would win if he did. He would win because he is connected to what Americans who aren't wealthy feel.
The lesson the party establishment needs to take from 2016 and 2020 is lesson they should have taken from 2008- if there's a grassroots insurgency against the establishment candidate, the insurgency doesn't always HAVE to be stopped- and if possible, those supporting the insurgent should be embraced by the party, not driven away and told to know their place.
Dems got that wrong with the Obama movement. They got that wrong with Bernie's supporters. Both were told to shut up and go away, the party suffered nothing but electoral disaster as a result.
Not every insurgent is going to have a George McGovern-in-1972-like showing if nominated- and the truth is, ANY possible Democratic nominee in 1972 would have lost at least nearly as badly as McGovern did- that election was over when Nixon did the China trip and when George Wallace was shot. No other Dem was going to get the Wallace vote, and when Wallace went out that vote was always going to go to Nixon as a bloc.