Right now no automatic solution exists. Also, I don't see any new solutions coming up in the short term.
This is mainly due to the fact that Apple does not allow apps to take screenshots of other apps running on your device. Therefore it is hard to get the information into the translation app. With the newest iOS versions it is possible for an app to record the screen of the iOS device as a video - given that the user has to enable it each time, and has to permit it. Video does not provide a good input source for this use case, as screenshots are much easier to process for OCR and automatic translation.
So unless Apple provides their own solution for this, it does seem that a slick solution is still some time away. However, it is always hard to predict - especially about the future.