Speaking in Brussels, Donald Tusk said that the approval of May's request for a brief Article 50 extension is 'possible' but would be conditional on a Commons vote in support of the withdrawal agreement (note: the agreement has already been twice rejected by the Commons, which has also already voted in favor of an extension). Meanwhile, Tusk said he 'does not foresee' an extra EU summit to focus on the Brexit catastrophe, though, if there's movement on passing the WA, he wouldn't rule out a meeting of the European Council.
In summary, Tusk said EU is prepared to let it go down to the wire - and if the UK can't pass May's withdrawal agreement, then no dice on the extension.