Looks like finally the big sized 21:9 ultrawide monitors are going to offer gaming specs, on par with the best panels, LG is launching its new Nano IPS panels line.
34 inch curved, 21:9 UltraWide LED Nano IPS, QHD 3440 x 1440, nVIDIA G-Sync 120 Hz (or Radeon Freesync 144Hz , LG 34GK950F model) Sphere Lighting, Multitasking, 1ms declared response time (Freesync model only) , covering 98% of the DCI-P3 color space.
And the incredible LG 34WK95U, a 5K panel with HDR 600:
34", 21:9 LED Nano IPS, HDR 600, 5120x2160, 5ms, Multitasking, Thunderbolt 3 Port (85W - 40GB/s) , 98% of the DCI-P3 color space.
Unfortunately these are not cheap monitors, hopefully going down sometime later.