"In answer to the question from the Scottish court, the Advocate General proposes that the Court of Justice should, in its future judgment, declare that Article 50 TEU allows the unilateral revocation of the notification of the intention to withdraw from the EU, until such time as the withdrawal agreement is formally concluded, provided that the revocation has been decided upon in accordance with the Member State's constitutional requirements, is formally notified to the European Council and does not involve an abusive practice."
While the Advocate General's decisions are non-binding on the CJEU, it is evident from past cases that the court tends to follow them in the majority of its final rulings.
With countdown days are plummeting towards the Brexit day on 29 March 2019, the court is expected to determine an emergency ruling within weeks but probably not until after the new year. If the court decides to endorse the AG's legal opinion, the case will be referred back to the court of session in Edinburgh for a final judgment.
Find the Press Release No 187/18 for the detailed opinion by the AG on the link below: https://curia.europa.eu/jcms/upload/docs/application/pdf/2018-12/cp180187en.pdf