There’s always the possibility of Johnson tabling a motion of no confidence in his own government, with the Tories abstaining. It would be surreal but isn’t everything at the moment?Johnson is going to treat a no deal victory for the Commons as a vote of no confidence in the government and call Parliament's bluff by requesting the two thirds majority for a general election.
It looks like a smart move.
But.
This has to have been anticipated, so my guess would be that the no deal motion will have a clause in it stating the government must request and secure an article 50 extension before requesting a general election, if that is passed then Johnson can request a general election all he likes, but Parliament won't give it to him because he's not done as they instructed on article 50. Johnson will refuse to extend article 50 and so the Commons will have had its hand "forced" and will bring down the government with a no confidence vote and it's hello interim government.
It seems that they’ve given up on the idea of forming an interim government. Too difficult to force Johnson out and agree who would be interim PM before time runs out.