PHP 7.4 is end-of-life, and so mysql 5.7. The real impetus for this change though is that openssl 1.1 itself (which both of these depend on) is going EOL in September as well. Most people hopefully won't be affected in any serious ways, but if you have PHP scripts on your site (such as wordpress) you should make sure you're up to date with the latest version.
I will likely perform this upgrade sometime next week, but depending on how busy I am, may postpone it slightly longer. I aim to have it done by the end of July in any case, so please check your site software for upgrades soon.
EDIT: Upgrade complete. Please upgrade your software if you have issues, and reach out to me if you can't resolve things.
Okay, upgrade is complete... I think. Let met know if you have problems. But please try upgrading any php based software first!