The supreme court ruled that the prorogation was unlawful. It is unclear what the implications of this are, besides that Parliament will sit for more days than expected and that future prorogations will be subject to similar scrutiny as to motive.
We seem to be in an interesting situation in which Parliament is divided on other-than-party lines (it is not aligned with itself). The executive can not pass legislation (at least not Brexit-inclined legislation) because it does not hold a majority. It can not get a majority because the Fixed Term Parliament Act prevents an election. However the speaker allows the (Remain) opposition to pass legislation which appears to bind the executive into specific courses of actions.
It is a very odd situation. Either parties must split and the Great Realignment occur, or else the issue on which they are split must resolve and the parties re-join and continue as they were.
Update: Raphael Hogarth explains the court’s reasoning.