I currently have a proposal for HTTP based real time notifications protocol called Events Query at the HTTPAPI working group at IETF based on the soon to be standardized HTTP QUERY method, which could provide a new mechanism for streams in Turbo. Think of Events Query as a more powerful and flexible SSE with the ability to stream notifications in any arbitrary format. In fact with Events Query you could, serve the HTML document and the change fragments all in one HTTP request.
If you prefer video, here is the link to my presentation at IETF 123: https://youtu.be/7MAg1EOjozE?t=2970
I also have a full set of javascript libraries to implement Events Query in both server and clients. so implementing this in Turbo should be pretty straight forward. The details can be found in the specification document linked above.
Thanks in advance for your comments or questions!