On 19 March 2018, the European Commission published the draft legal text of a withdrawal agreement. The draft highlights the progress which has been made in the negotiations which took place between the UK and the Commission on 16-18 March 2018. If agreed and ratified in its current form, Article 121 provides for a transitional period for Brexit to 31 December 2020.
The Commission has also proposed the ongoing jurisdiction of the Court of Justice of the European Union (CJEU) over matters referred to it before the end of the transitional period. If agreed, then there would still be time for the UK courts to make further references the CJEU (as in Cambridge University, discussed further below) and for the Commission to pursue infraction proceedings against the UK.
A copy of the draft agreement is available to view here.