WordPress 5.3 came out a couple of months ago and PHP 7.4 came out last month, but the server won’t be getting updated to those just yet. It’s always safer to defer updating things for a while since updates often have unintended problems (Microsoft has certainly proven that with Windows 10 in the past few years). Since developers don’t seem to bother doing testing anymore, it’s better to wait until other people play guinea-pig before upgrading. (Also, PHP 7.4 doesnt’ seem to be available in the Pi/Buster repository yet and I”m not inclined to use third-party repositories anymore.)
The server is (more or less) stable right now and changing things almost always reduces that, so as they say, if it ain’t broke, don’t fix it.