For images at low bit per pixel, HEIC is actually quite a bit better than JPEG-XL current encoder. I wouldn't say really an upgrade technically speaking, I would put them on same level with XL have some additional interesting feature.

But considering getting HEIC included in other system seems to be difficult due to patents or other reasons. JPEG-XL seems to be the best middle ground in everything.

I am still hoping there could be additional work on JXL in terms of low bit per pixel improvement and encoding / decoding resource usage. Especially in the lossless front.