The ECJ is set to hear the Article 50 case today (HERE). This will determine if the government can unilaterally revoke Article 50 and perhaps give MPs who are opposed to Brexit another option. It is not a given that the ECJ will find in favour. If countries in the EU are all able to send in Article 50 notifications and then withdraw them willy-nilly it would make a mockery of the whole process and hand them a cudgel to beat the Commission with.
If they do find in our favour, I expect there to be plenty of caveats - perhaps including a new referendum - to dissuade governments from wasting an awful lot of time and effort in order to secure some concession or other from Brussels.
If you want to read the government's grounds for their appeal to the Supreme Court, which they lost, you can read it HERE. Essentially, they were arguing it was hypothetical because they did not intend to revoke the notice.
However, that was then this is now.
