If you had kids, and an iPad, they may try to unlock it themselves. You may run into a situation where you see something like this
In this case, there are two things you can do. Well, besides waiting 1 million years.
If you have find my iPhone set up you can remotely wipe it. That works if the iPad is connected to Wifi.
If you have your computer, you can connect it, open iTunes and hard reset it. iTunes will ask you to update or restore. Restore it. You can then set it up fresh or restore from backup once it comes back up
Seems like this is a problem that should be solvable somehow 🙂