I think the first priority at the moment is to complete the draft of the scribble protocol type syntax doc.
However this should now be able to include the new choice construct, although I am not sure how widely the 'introduces' construct has been discusssed? Has a syntax been agreed for this? If so, then it could also be included in the draft.
Once the draft is ready, given that we are planning on a discussion/comment period of a month, that would probably be a good time to update the syntax/model - and then do one more release after the final version is agreed.