After several proofs with my Designer Team, we have decided to store full image resolution with transparency with JPG-XL, it doesn't matter if Adobe does not support it, we have plenty of alternatives to get any kind of size and format from it.
However it would be a great improvement if PSD are by default compressed in JPEG-XL, if the latter is integrated in all the Adobe Products, for what is my concern inDesign and Illustrator, but it is good for the web as well.
Here my test:
JPEG-XL is the smaller format while still preserves losseless high quality pixels and transparency. It outperforms JPG "HQ" which is our alternative to the venerable format to PSD. WEBP also outperforms JPEG, but the format is limited in many ways, also it can be shutdown by its own creator anytime soon, it is really an unreliable technology on what I won't bet all.
We can leverage the right technology if we can make our voice loud. There is not any need to please another company, perhaps a partner, against the good and the will of its own users and customers.
Please do the right thing!