This KB would help you to if you should enable mysql_native_password when upgrading your mysql database.
To decide if you need to enable mysql_native_password, check if users are using mysql_native_password by logging in your current database. can use the query below:
SELECT user, host, plugin FROM mysql.user;
If you see a user using mysql_native_password please enable when you upgrade to 8.4 to avoid downtime.