You won't ever fully replace GIF, at least not in the next decade. There are too many devices and apps/software that ONLY have GIF support due to the low computational footprint (designed for 1989 hardware). There's a reason why all these sites that have replaced GIF with HTML5 video still have a GIF fallback available. The file size is usually much larger, but it is supported everywhere. 100% of devices will be able to support GIFs. It's hard to argue with universal support.
Also, FLIF is much better than APNG, animated WebP, MNG, etc. If we are going to adopt a new universal standard as a replacement, that's the smarter route.
This is good news though; finally we can start to abandon the cruddy old GIF format and move to something more modern.