As long as they have it on their radar, I will remain cautiously optimistic.
Considering the fact that this tech is around for at least a decade and is part of almost all commercial renderers (and the VFX platform specification) I don’t think this is an extremely hard problem to solve.
If they plan to implement it into EEVEE, that probably makes it easier to implement it into Cycles too. I could imagine that the back-end is the same, just the way how it interfaces with the render engine is different.
Probably because people take it for granted and never actually think about it since it is the status quo.
I only discovered it in action by really paying very close attention to my VRAM usage when comparing Arnold and Cycles a while ago.
I didn’t now that it is called on demand mipmapping (instead of normal mipmapping) until 3 months ago when it popped up in the Blender 4.x Cycles Photorealism Improvements thread.