The question now is how much of AVIF's advantage comes from the encoder compared to the image format itself. If it is the encoder, does JPEG XL even stand a chance of catching up? AVIF will certainly receive further improvements, albeit at a diminishing rate.

https://giannirosato.com/blog/post/case-against-jxl/ suggests JXL is fundamentally limited. We'll see. There's a race on and it's great!