There is a very simple fact which is overlooked:
- JPEG: has substance
- "JPEG 2000", "JPEG XL", etc. (everything coming from ISO WG1): have no substance
The substance of JPEG is in four fundamental properties for image representation.
Upcoming JPEG 10 will enable backward compatible HDR support, as announced in the infancy article.
Lossless transcoding of JPEG for smaller file sizes can already be done with jpegtran or Jpegcrop.
It is called arithmetic coding.
See also my recent post here.
You could add any other entropy coding method with lossless transcoding to JPEG if you are really interested in the feature.
The fact that they do not add it to JPEG but to an otherwise unusable format shows that they are not really interested in making such feature usable.
Arithmetic encoded or transcoded JPEG is at least usable.
I use it since many years for almost all my local JPEG images.
That's why it is the default setting in Jpegcrop.
Regards
Guido
JPEG developer