I feel your pain as I still have an iPad 1, but I don't really expect devs to still support it.
New OS updates.... well I guess I would say if you're not going to update the game so it still works you should pull it from the store.
Because what we're talking about here is you buy the latest iPhone and you buy and download a game currently available off the App Store and it doesn't work.
So, in other words... video games lately!
This ecosystem has needed a compatibility flag of some kind ever since iPad 2 compatible games started using the presence of a camera as their hardware determinant.