There are some other things transpiring in American politics right now. But we must note that Democratic leaders are now unabashedly stating what Bernie Sanders supporters said over and over in 2020: the party pushed Joe Biden primarily to stop Bernie.
I’m not sure we should be so pessimistic yet. They blocked a candidate but did nothing to kill it’s popularity. As long as we don’t succumb to Fascism within the next four years, there’s still a massive base of voters that would vote for a socialist in the '28 primary, and the left democrats will have had 12 years since Bernie’s first campaign to build up the infrastructure for it by that point.