Hi NickolaiKorzan-3179,
SQL Server 2016 is in extended support phase, in this phase, the software still requires product’s supported service pack for full support (including security and DST updates)
But unfortunately it is uncertain when CU18 will be release, it depends on the official arrangement.
When support for a service pack ends, Microsoft no longer provides new security updates, DST updates, or other non-security updates for that service pack, and you know support for SP2 ends in Oct 2022. No one knows if there will be additional official arrangements in the meantime