yeah exactly, "4k" is a term I think anybody who downloads textures or makes textures is familiar with given they are, mostly, made in a 1:1 ratio. They're not using it incorrectly as if you made a 4096 texture and divided it into 4 parts it would display as created (in theory). If anything loads of brands in SL use the term "HD" in a disingenuous manner.
4k in tv terms just means 4 times as many pixels than standard "HD TV" (thanks google).
Most people will already make textures in 4096 and then resize or let SL resize. If you want to test go download a 2k texture and a 4k texture and upload them both and you'll notice differences. Anybody using software such as blender or substance will bake in 4096. You could even bake in 8k but working with images that big (and the storage) is a nightmare.
I'm glad somebody is doing something and who knows with pbr around the corner maybe this will take off - I mean imagine making a material of say glitter on the face. Part of me imagines the "4k" texture stuff will appeal to the detailed images types on flickr.
Also with regards to creators, this could mean that a lot could simply take their original SLUV skins (lets presume they made them in 4k) and just divide into 4 parts. No reason loads could not update half their back catalogue in a few days (can't they just create a PS action?) and charge a few linden at weekend sales for the benefit. Somebody already showed a nice looking sessions skin, imagine how good those might look in 4k.