The issue is that parliament made article 50 statute. It would therefore take another act of statute to revoke it, as I understand it, that needs a motion passing by both houses. It would take time to do this so it can't be used as a last minute ploy. There are no plans to introduce a motion to revoke article 50 from the government. It's possible that somebody from the floor could bring such a motion, but if it were even possible to make that statute (which I'm not sure tbh) it would set new precedents in Parliament for creating laws, and I'm not sure that a majority of MPs would want to go there/
The way the Govt is heading with this is, initially, to vote against a no deal. If they lose this motion, which is unlikely, we will leave on 29 March with no deal. If the motion is passed they will then bring forward a motion to apply to the EU for an extension. If that motion fails, or if the EU say no to an extension, then the fall back is that we leave the EU without a deal.
Effectively, parliament has allowed the country to get itself into a position whereby the EU is effectively in control of whether or not we leave without a deal. Unbelievable really. If the EU didn't have us by the balls before they have now.