Well, everything will still work. It’s just if there are problems or if someone can find a way to compromise SQL Server 2008/2008r2, Microsoft is not going to fix it. It is best to upgrade to a newer version that Microsoft does support and update on a regular basis. If you are using an SQL Express version, this is fairly simple. If you are using a paid version, then you will need to purchase a new version. The new version must be compatible with your programs as well.
It’s always best to keep everything updated when it comes to your network. This will allow you to have the latest security updates and is the best possible way to not have your network compromised.
Stay safe out there!