Some queue functionality was added in version 2 of the transport API:
The queue functions are:
Support for subscribing to the play queue for a specific zone
Support for playing from specific points in the play queue for that zone
The matching functions are subscribe_queue and play_from_here. I haven’t tried them myself but my guess would be that the first gives you a list with the items in the queue, each with a queue_item_id which you then can supply to the second function to start playback from a certain point. These functions could provide functionality to show what plays next and things like that.
Unfortunately jsdoc comments haven’t been added to these new functions yet, so some experimenting is probably required.
I managed to do just what you said with those two functions. I can list upcoming queue items, get queue change events and play from specific item in queue. The rest regarding the queue, I think, is not possible (yet).