The bets are placed. Both YouTube and Netflix have named AV1 a video codec for the future: Google’s video service is already using it on TestTube (new, experimental features for YouTube). Netflix has been calling AV1 “our primary next-gen codec” for a while now.
AV1 is a new codec that produces videos 30-50% smaller than H.264 and 30% smaller than H.265. It’s already supported by Chrome and Firefox (with Edge support in beta), so it’s not too early to start encoding your videos with it.
This article helps you get started encoding with AV1 and has a great tip at the end to convert existing GIFs to it (reducing their size by 20 to 40 times)!