I think between the revolutionary crowd, the university students, and the far-right crowd....yes, there will be enough votes to carry the measure.
Beyond that step? I don’t think any method exists to allow them to leave. I personally would like for them to find a method, allowing them to exit and for the Jefferson-state crowd to re-enter the US as it’s own state, with the remainder on a two-year hike to bankruptcy.
Without Jefferson, what will they do for pot?
Secession is not unconstitutional. At all, in the least.