We do not have any current plans to increase MySQL requirements yet. However Joomla 5 requires MySQL 8. So you will not be able to update to Joomla 5 without moving servers to one that provides MySQL 8 or its MariaDB equivalent 10.4.0. The banner is a heads up notice that in a future stable release we will likely have to increase our minimum to remain compatible with Joomla 5. However there's no urgency as we'll continue to support Joomla 4 until it is completely EOL in 2025. We'll likely take down the notice since it seams to be causing too much confusion.