There is written a lot in linked issues/prs.
#23118

But TBH: I don't understand finally which use line we shall use now...

Joomla\CMS\Image\Image is the one to use, the Framework package was deprecated after pulling in that code in the CMS and the deprecations were never updated.

Thanks @ReLater and @mbabker

@Ruud68 can you send a PR to update the deprecation message?

I have no idea if and what the message should be. For me it is clear that I should use \Joomla\CMS\Image\Image if my extensions should work on both J3 and J4. if that will get deprecated in 5.0 or not: I do not know (according to J3 it does, according to J4 it doesn't)

Right now Joomla\CMS\Image\Image is not going anywhere. The deprecations in the Joomla\CMS\Image namespace that explicitly say to use the joomla/image Composer package and classes in the Joomla\Image namespace should go away. The Composer package will go EOL the same time that the 3.x CMS branch does.

What will go away in 5.0 is the class name aliases (all the non-namespaced class names). That's not changing unless someone suddenly decides "keep aliases forever".

Whether or not that API is deprecated in the lifetime of 4.x and removed in 5.0 is anyone's guess, unless you've got a crystal ball (in which case, I need to borrow it, for... reasons...).

Can un-deprecations be made in a patch release or do they have to go in a minor? Semver doesn't mention anything about such thing.