I don’t think Boris will call an election until after we’ve left on Oct 31.
There could be a vote of no confidence but the government could quite easily win it.
Many Labour MPs are also shit scared of an election if brexit has been frustrated again.
Even if Boris did ask for an election, the chances of getting the necessary 67% of MPs to back it is far from certain.
I suspect the most likely scenario is Johnson returns without the EU offering substantial change by September.
There will be half arsed attempts to bring forward “motions” to stop any particular course of action...just like last time - which will hold no weight.
Remember parliament has already had a vote on all the options, including 2nd referendum, customs union, deal, no deal etc have all been voted down in the past.
possibly then, there will a vote of no confidence which could pass, or it could fail.
Even If it passes, it is very unlikely that there will be time to cal an election and get it through parliament by the requisite majority required and then hold that election before oct 31.
Also, Johnson is unlikely to be forced out and no alternative PM is likely to be able to command a majority either.
No deal is very, very likely now - almost certain.