Curry's and John Lewis currently have the Samsung Q90 at £2,199, so there's definitely room for them to go lower, but there's no way of knowing when.
https://www.johnlewis.com/samsung-qe65q ... lsrc=aw.dsLG and Sony's OLEDs offer marginally better picture quality but they can't get as bright so may not be the best option for a brightly lit room, and you may be paying for features you don't need (in Sony's case sound that emanates directly from the screen, or LG's top end model comes with a sound bar attached, neither of which however are as good as a dedicated sound bar or fully fledged sound system). OLED TVs are the ultimate way to watch a movie, and LG's response time for videogaming is superb (better than Sony, though how many people notice is negligible), but there is a small risk of the picture burning into the screen, so not great if you're watching a lot of bold, static graphics for hours at a time.
To be honest, whatever flagship TV you choose from the big 5 (Samsung, LG, Sony, Panasonic and Philips) you're not going to end up with a bad TV. It's the mid and lower ranges where it becomes really complicated, especially as some manufacturers have started doing store-exclusive models making it extremely difficult to compare.
In terms of a roadmap, 2020 and 2021 will see all the manufacturers adopting the latest standards for the PS5 and new Xbox (such as HDMI 2.1, higher framerates, 120Hz, HDR10+/Dolby Vision) and 2022 is when you'll be seeing a lot of 8K TVs (only Samsung has an 'affordable' one out right now).