As of April 1, 2020, 538 makes this prediction: No one will beat Sanders!

[The Magistrate]

8. That Is Really Not Quite True, Ma'am

Everyone has the right to vote in the general election.

Primaries are affairs of a private organization, which could change its rules if it chose. If the party chose, for instance, to select delegates to the convention by a slating committee, or by nomination at a state convention to which only people elected to office as Party members, or who held a position in the Party organization, were invited, there would not be the slightest recourse. Even in states where a primary is mandated or supervised under state law, nothing obliges the Party to abide by its results.