This CAN happen to any iOS device, particularly so with any iPad model, at any time.
Especially problematic if you are always using your iPad, iPhond or Watch at full, 100% screen brightness, all the time.
Here's what I advise for any iOS device with screen image burn-in, “image persistance” issues,
Charge the device to 100%.
Completely power down the iPhone/IPad.
Un-pair the Watch from your iPhone. Fully power down the Watch.
DO NOT use or turn on the Apple device for 3-4 days to let the screen pixels have enough time to “de-energise”.
Five days, I feel, is ideal, but 3-4 days of powered down, non-use is, usually, sufficient enough.
If you turn on the device prematurely and screen burn-in/“image persistance” is still noticeable, you will only have to do this entire full procedure for another 3-4 days.
If this works, the screen burn-in/“image persistance” should NOT return for some time.
This has happened to me with all of my iOS devices, at one time or another, and with iPhones and iPads, I had to go the full straight 4 days to get rid of the screen burn-in.
It usually comes back anywhere between 9 months to two years, or so.
Hasnt happened on any of my devices, so far,,to date, but I keep my screen brightness on all my iOS devices around the 50%-75% range to minimise the image persistence risk.
Best of Luck to You!