Check out the key dates for Salesforce Winter '20. Sandbox Previews started on September 6th. Production release will be happening the first two weekends of October.
Details on Page 5.
NA51, NA56, NA63: November 3, 2019, 08:00 - 12:00 UTC
NA32, NA53, NA60: January 19, 2020, 03:00 - 07:00 UTC
See page 7.
Instance Name Changes
November 3, 2019, 08:00 - 12:00 UTC
NA51 --> NA118 or NA126
NA56 --> NA120 or NA121
NA63 --> NA134 or NA171
January 19, 2020, 03:00 - 07:00 UTC
NA32 --> TBD at least six weeks before
NA53 --> TBD at least six weeks before
NA60 --> TBD at least six weeks before
See pages 8 for details.
Salesforce Mobile Web Experience: Previously, you could experience Salesforce on your mobile device via the downloadable mobile app or through your mobile web browser. Starting with Salesforce Summer '20, you will need to download the Salesforce app to access your Salesforce data on mobile devices. See page 27 for details.