No one here works for Apple.
I am just a user, like you, who volunteers my time here to help out fellow Apple product users.
That iPad Mini is over 6 years old.
As I stated, you still have another full year ( 2021 ) of third party iOS app support and even after third party app supports goes away, you could still use that iPad easily for another, additional year, or so.
That iPad is DONE getting ANY other new, major iOS/iPadOS system support other than minor security updates to iOS 12.
Still many iOS 12 supported apps still available from the Apple iOS App Store.
So, it is still entirely your decision what you want/wish to do.
I cannot make that decision for you.
That iPad is still perfectly usable.
Apple will probably NOT give you very much money for an over 6-year old iPad for trade for s new iPad.
You'd be better off keeping that iPad as a secondary iPad and purchase another new iPad.
Best of Luck to You!