This information is now being distributed in a number of KBA documents that you can view while logged into SAP Support portal https://support.sap.com. The two main KBAs are
http://service.sap.com/sap/support/notes/2075653 - the release schedule for 16.x
and
http://service.sap.com/sap/support/notes/2077419- the release schedule for 15.x
In both documents is a list of the individual rollup/patch level releases with past and future planned release dates, with a link to another document listing change requests (CRs) targeted for that release. You can subscribe to these KBAs to be notified when they are updated by clicking on the "subscribe" link at the top of the page.
