I moved your post to an already running suggestion thread requesting this feature.
Don’t forget that you need to click the like button on the first post in this thread to show your support for this suggestion! 
I have a Question about this, because I see it’s currently „in Progress“:
Does this also apply to pinned items on the home screen? For example, if you pin a collection to the home screen, it currently only shows 20 posters. Will this number increase (as it used to)?
I’m guess the fact that we requested this 6 years ago, and it’s not been done so far, there’s no interest in doing it. Maybe it’s harder to do than it would seem.
@james is this Suggestion also apply to the pinnend Items? Or is there another Threat for that?
Today’s 8.4 update has increased the max watching list count to 40 items. 
But is it also planned to increase the pinned Items on Homescreen?
The up next list cap is 40. Much much better than the 15 limit before! Thank you @james
Could you add a “see all” option at the end to have a full list?
great suggestion