Jeremy Corbyn may want to be World King (sorry, I just can't get over Boris Johnson's early description of his own ambitions) and hold a GE after that, but...
To become WK he needs 50%+1 of MPs
To get a GE under the FTPA he needs 66% of MPs.
And you can bet anything JC knows this. So he can be WK, try for an election, then when that fails he can say "oopsie, guess I'm your PM until 2022 then..."