37-42"
1920x1080/1200
VA/IPS
AG/matte screen surface (matte bezel preferable, as well)
fast pixel response time (no smearing)
low input lag
8bit colors (no dithering), standard gamut
100Hz+
FreeSync, with LFC and good range (30-100Hz / 40-144Hz)
Curved (1800R is enough, not sure whether 1500R would be too drastic)
AmbiLight or similar (preferably dynamic, but if IP rights are a problem, then static is OK, as well)
PWM-free (both backlight and ambient light)
Ergonomic stand (no portrait necessary, though)
DisplayPort + HDMI
800€ (/£700)
I currently have the Acer XZ321Q, which includes quite a lot of these. So I'd say 800€ should be fairly doable, considering it will take a while before you would get the new monitor out, so it will be a different market then.
Few additional notes/clarifications:
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Panel type:
Either IPS with improved blacks and no glow, or VA with faster pixel response time. Of the current offerings, I would be inclined to go with VA. But for obvious reasons, LG is most probably looking at IPS. In which case, try to develop a better IPS with less glow and deeper blacks. Otherwise I'll just stick to VA, with its slightly inferior pixel response time. Likewise VA's viewing angles are currently good enough, especially with a curved screen.
Resolution and aspect ratio:
Personally, 1920x1080/1200 is more than enough for me (I used to have 42" 1080p, which was a good combo), but I understand most people would prefer more for bigger sized panels. And 16:10 would indeed be nice, as I prefer more vertical space over excess horizontal. But I understand this would bring extra costs, so I'm content with 16:9. (would pay ~100€ extra for 16:10)
Things of no concern:
First and foremost: chassis depth/thinness is not a concern! The change from CRT to LCD was enough. Anything thinner than 15cm is good enough. No need to go overboard, especially if it affects other areas (like backlight bleed, screen uniformity, etc.). Although, THIN bezels are nice, but still not worth any extra compromises, though. Not that bothered with HDR, but might be willing to pay up to 200€ more for it, if it were included. Don't care about speakers, you can leave them off, too. You can also scrap the VGA connector.
As for local dimming:
In theory: yes, a nice feature. Just make sure the transition phase is fast enough, so that we can't see the left-over white backlight from an earlier bright scene, showing up as grey on the dark scene. If you can't manage this, then I'd rather take a fixed backlight with better blacks (like VA). Technology is only as good as its weakest link. So don't try to over-achieve something expensive if you're just fumbling it with a crappy implementation.