Talking to Yamaha at the Blackpool keyboard Festival UK where the S900 was played in concert and also demonstrated, the release date is end June/early July in the UK.
As usual I bought up the subject of 76 notes, and as usual the reply was the same, Yamaha has researched their intended market of arranger keyboards (Home Users) and there is not enough demand for a 76 note version.
So don’t expect one anytime soon.

Bill