Good question.
It's difficult to see how Labour can move on with the ban whilst also claiming to be implementing the recommendations in Cass.
I think this is actually a golden opportunity for Labour (particularly if Starmer has been privately panicking about trans issues and looking for a way to subtly row back on his previous position) to say, "This changes everything. We know things now that we didn't know before. We need to ensure that young trans people are getting the best quality care in accordance with the best available evidence."
And if Labour doesn't do that, it will be easier to hold their feet to the fire. It will be easier for any MP in parliament opposing the ban to stand up and say, "What about Cass?"
The House of Lords will say, "What about Cass?"
Mumsnetters protesting outside parliament will say, "What about Cass?"
The point at which it becomes easier to drop the conversion therapy ban than to proceed with it is the point at which they will drop it.