AV1 has been becoming a more and more popular codec for not just streamers, but also content creators and filmmakers. Video hosting platforms, such as YouTube, are now implementing AV1 as a way to easily stream video content to audiences at lower bandwidths. Filmmakers, and especially content creators, are asking for AV1 for creating high quality content without too much compromise for file sizes and ease of use when viewing.
Having the benefit of AV1 video will help with preserving the best image quality at a much smaller and efficient file size than codecs like H.264. HEVC/H.265 is supported in Premiere Pro and it's a very nice codec. In fact, both HEVC and AV1 perform very similarly. However, it would be wonderful to have the flexibility of additional codecs that are gaining traction in modern media.
HEVC isn't supported everywhere, largely due to their licensing slowing down adoption. Meanwhile, AV1 is open source, so it would be easier to adopt without the concern for licensing; thus, making it more popular with platforms than HEVC.
Competing video editing platforms have also supported AV1 encoding and decoding for some time and I have been wanting Adobe to look into it for a while.
Overall, I highly recommend Adobe include AV1 encoding and decoding support for Premiere Pro. I strongly believe it will heavily encourage more people to create the best content with a codec that is extremely efficient as it is excellent at preserving image quality.