For me the problem isn't that colours in the game are oversaturated but that the colour tempature is too warm/yellow-ish. It's been that way ever since the January gameplay. This what not an issue I noticed in the 35 minute demo nor the SoD trailer.
If you recall the previous Witcher games the REDs love to play with different light temperatures, colours and various settings wich go hand in hand with that.
If you have a look at that poster at 2:05:
You'll see that all the regions have very different light settings.
The yellow palette is part of the wealthy pre-war Nowigrad and the pacified northern Temeria White Orchard area, so it's my guess that we'll get a lot of different lighting areas. Wich will make it awfully hard to have a SweetFX set that looks good everywhere
But you're right compared to the older shots the colours got brighter, still the Art Direction tries to get a certain vibe for each area, so that's definetly one of the things that should be judged at runtime not from random screenshots. Maybe the bright colourful vibe is the equivalent to the Act 4 area, meant for the player to relax? But I'm probably just repeating older arguments.
I wouldn't worry too much about it for now and wayt until I got my hands on. (I'm also no friend of the plastic-ish look of modern games, but that's nothing that can't be fixed easily)