I was looking at the Steam Hardware Survey and just 2% of people game in 4K and 6% at 2560x1440. 65% still play in standard 1080p. 4K is still way too expensive and far too costly in terms of performance on most games. 2K is a nice sweet spot if you have a good GPU - some users would rather play at 140+ frames at 1080p at higher settings rather than 50fps+ on lowered settings at 1440p.
I think 1440p gaming will become very popular in PC gaming in the next 3 years especially with quality monitors being so affordable plus improved panel variety, quality and performance so you aren't tied to primarily just to TN's. Hardcore competitive gamers will probably remain behind and lap up the 280hz/360hz new monitors that will be coming into the market. Casual gamers will definitely be looking for 1440p 144hz 1ms IPS type monitors for around the £300-400 mark.
High end gaming is definitely not worth it unless you have money to burn and people will always be priced out. The GPU market never moves down in price significantly when new series of cards are released because the old ones are still viable. High end gamers will always have to spend £2000+, midrange is usually £1200-1500 and low end is between £650-1000. The market doesn't change massively even if the tech does.