My guess is an overwhelming (but utterly non-binding) rejection of 'no deal' by Parliament tomorrow, followed by a large majority on Thursday asking for a short-term extension of Article 50 to try to sort something out, followed by the EU saying "a year or nothing", followed by public disagreements, followed by an agreement for an extension of between two months and a year. Nobody actually wants a chaotic exit except a few financiers, and we're doing enough damage to ourselves that I doubt the EU wants to enforce a punishment beating at a cost to their own member states' economies.
As for the final outcome, I'd guess:
* No deal (10%)
* May's deal (10%)
* New (softer) deal (40%)
* Second referendum (40%), with any option possible after that from no Brexit at all to the public saying 'sod you all' and demanding a no deal exit.
But anything's possible at this point; we're off the map and predictions on the process I was much more confident on have already been wrong.