I have mixed feelings on this.
Bad feelings first. Bernie staying in keeps the citizenry aware of the proponents of socialism as Bernie and his like proudly carry it on their chest like a medal of honor. Now there will be more of a subterfuge socialism carried by Biden or whoever the Dems nominate, incrementalism by dying of a thousand socialism cuts one might say rather than the whole shebang at once. The subterfuge strategy is much more dangerous as it has a better chance of reaching the same goals with a different modus operandi.
The other bad news is that this just might mitigate Bernie being a 3rd party spoiler for the Dems similar to Nader in 2000 and 2004 who denied Dem votes to Gore and Kerry.
Now the good news. I think in a head to head matchup with Biden and no Bernie 3rd party, the chances of Trump getting the popular vote majority rather than just a plurality is strengthened. It is wonderfully ironic if Trump could get the majority popular vote and those states that signed up for National Popular Vote Interstate Compact have their electoral votes go to Trump.
For example, I bet there would be some decidedly irate true libs in the state of California if the state awarded its electoral votes to Trump in spite of California citizenry overwhelmingly casting ballots for the Dem ticket.