My take on the Brexit mess as at 1330 12th March.
Scenario 1 - Mays “new” deal passes, there is a short delay to Brexit while all the legislation is passed. Then we enter negotiations with the EU on our future trade relations. This will probably drag on past the cutoff date and the “backstop” will kick in. This will mean the UK as a whole remaining in a customs union until the trade stuff is worked out. Could be years. UNLIKELY.
Scenario 2 - Mays deal fails, she cancels the votes on Thursday and Friday because she insists whe can get even better terms from the EU and will return for a 3rd vote on the 26th (i.e., just before a no-deal Brexit). This will go down like the proverbial lead balloon and parliament will insist on going ahead with the two votes. Since this would mean that the PM is a proven liar and con artist., hence UNLIKELY,
Scenario 3 - Mays deal fails, and she honours her commitment to hold the Thursday and Friday votes. Both of which are positive. We ask the EU for more time, they say a few months is no good and insist we opt for a 21 month delay so that this gives enough time for (a) a referendum on Mays deal/no Brexit and/or (b) a general election or (best of all) © no Brexit, because everyone has lost interest. PROBABLE.
Scenario 4 - Taking advantage of the incalculable blind stupidity of the human race, aliens invade, establish Utopia and everyone lives happily ever after. YOU NEVER KNOW.