Meaning:
Jolla themselfs don't know what version it will be up to this point

Speculating,
the anouncement alone implies they are quite confident to get any newer version running.

Hoping,
they have a newer version than 4.4 running already but are still testing with even newer versions.

Fanboy-level,
they are testing top-down, got Popcorn running but do not believe themself and can not stop testing and might fall back to Oreo if they hit a wall