Honestly, I tuned out. Animations are procedural and are best represented with a scripting language - not with a declarative image format. Resource-constraining javascript within an (i)frame is probably a better way to spend a browser developer's time.
I believe there is a niche for simple animations: just a sequence of frames in a loop. No need for JavaScript, since it's just a simple loop. Easy to upload to image hosting services. And all browsers already support such simple-loop animated GIFs, so the code is already there, just not utilized to full (true color) potential.
This is true for the majority of animations, but .gifs have come to serve a niche for short video content sans audio that they uniquely fulfill on the web. If APNG or MNG or whatever could replace huge animated .gifs for things like r/cinemagraphs I'd be thrilled.
Having seen animated gifs, I can assure you that mngs (pronounced as mings) would be likewise huge. It's better to just have a 1-line JS script do this, and a standard for sandboxing nonthreatening JS.
But you can't upload that 1-line JS script to imgur.
Animated GIFs are getting very popular again because even with 5Mb-8Mb sizes GIFs are easier to handle today, comparing to downloading that 200Kb Dancing_Baby.gif in the 90s.
Animated GIFs are still humongous and slow to load, even with today's fast network links... Surely one of the bet reasons to replace them is to actually do a bit better.
The type of deltas used in GIF can be easily implemented as it's the standard alpha blending method, available at OS and GPU level. Can't say that about more complex delta-PNG algorithm from MNG spec.
