It still all sounds very vague to me, and I don't trust preview impressions when we don't truly know what screenshots are being taken at. CDPR has been repeating the "mix of Ultra and High" rhetoric without specifying what's what while also stating they haven't truly shown Ultra and want people to be blown away on release.
I don't necessarily think they're lying, but mostly believe Ultra includes demanding settings related to resolution and anti-aliasing, expensive stuff that most people don't crank stupidly high if it comes at a cost of performance. Foliage, shadows, textures, etc; I cant see why they'd have superior settings to marketing material (supersampled marketing material at that) kept hidden for no good reason. Especially why they're also happy to demonstrate expensive effects like Hairworks.
CDPR occasionally has miscommunication between departments, so yeah, I just don't buy the idea that significant asset and effect related rendering settings have been kept on High for marketing material while Ultra has to wait until release. I can't think of any other developer/publisher doing this nor can see any advantage. I could
maybe buy the theory that they want to keep polarity with a console release if Microsoft or Sony were publisher. But while they might have a promotion deal with the former publishing is done by neither. It's against Bandai Namco and Warner Bros interest to market a game looking worse than it supposedly does...but also at the same time having those worse settings shown in supersampled screenshots and 4K.
I'm running with the 4K screenshot they released. It seems to be a gameplay shot, HUD turned off, no fancy camera angling. With downsampling to 1080p, I can't see Ultra looking any better.
Not that I care because it's gorgeous.