As you know this can change. However, the target availability for SP11 is estimated to be 7/16/2021.
What to Expect
More Ribbon Improvements -
Since the changes in SP10 were primarily user interface-related with very little code changes, publishing a list of changes would've been a waste of time. Instead, that list will be published on or after SP11 is published.
The last service pack was left unannounced because I wanted to make absolutely sure the new coding was stable before I mentioned it was available. Based on the feedback I've got thus far, it appears to be solid, which is great to know after several years of going without updating the software. (THAT won't happen again... Ever.)