He sounds like a sore loser who is on the brink of telling Democrats to fuck off and run as an independent candidate.
He wouldn't do that, too transparent. He might continue to poison the well, give some strong nods to Stein and the Green Party, then endorse Clinton at the last possible minute to stay in good standing with the DNC. Then his "revolution" would be that extra bit needed to get a GOP POTUS and he can run again in 4 years when the "revolution" would be truly ready.
Sanders is a politician, he's been in office almost his entire life. He isn't going to run independent and sacrifice all relevance in the senate.