Originally, the Support for Exchange Server 2010 will end on 14.01.2020. Microsoft has now extended support until 13.10.2020. One of the reasons for the extension of extended support is apparently the many installations that are still active or organizations that are currently still busy with the migration.
Here you can find the article on the Exchange Team Blog:
Incidentally, the extension of support only applies to Exchange Server 2010, not to Office 2010 or SharePoint 2010. Support for Windows Server 2008 (with/without R2) still ends on 14.01.2020. Exchange 2010 security updates will continue to be available as required after January 2020, while the Windows Server 2008 operating system will no longer receive updates. However, Exchange 2010 is also supported on Windows Server 2012 (with and without R2).
Anyone running Exchange 2010 on Windows Server 2012 now has until October 2020 to complete the migration to Exchange 2016 or Office 365. Migration from Exchange 2010 to Exchange 2019 is only possible with the intermediate step Exchange 2013/2016.