I just stumbled across this on the Delta agency website. I hadn't heard anything about it yet and it seems to have gone live today. Apologies if I missed FT leaking this info early
https://pro.delta.com/content/agency...-s--class.html
They are adding a new rbd (S) for Comfort+ bookings; looks like it will be a lower class than W. Fare basis will use I in place of C. Looks like this went live for published inventory today.