I recently updated my iPhone to iOS 11.0.2 and I simply lost almost all the games that I "owned" in it. And, as far as I understand, unless the companies release an updated version of these games, they will never be accessible anymore.
The main problem is that many of them will not receive such an update. Mainly because the publishing company doesn't have the rights to it anymore, because the publisher doesn't exist anymore or for some other reason.
This is one of the main reasons why I hate digital only games and NEVER pay for a game that is not released in physical form.
(The only downside to it is that it seems that I will never be able to play Sonic Mania, haha.)