PS4 Pro 4 released in 2016 , Nintendo Switch released 2017 & Xbox One X released 2017
PS4 Pro / Xbox One X main selling point is that they are 4K versions of PS4 / Xbox One & I doubt if either one of them has sold 10 million units yet but Nintendo Switch can barely do 1080P when docked but Switch is somewhere around 28 million sold as of now & there is nothing standing in it's way or making it to 40 - 50 million by time the PS5 & Xbox Next come out. Also Xbox One S & Xbox One X both play 4K UHD Blu-rays but no one really care.
Next generation is the time to make a move like Nintendo made with the Wii & Switch because not enough people will care about 4K in 2020 the same way the none HD market was still bigger than the HD market in 2006.
PS4 Pro / Xbox One X main selling point is that they are 4K versions of PS4 / Xbox One & I doubt if either one of them has sold 10 million units yet but Nintendo Switch can barely do 1080P when docked but Switch is somewhere around 28 million sold as of now & there is nothing standing in it's way or making it to 40 - 50 million by time the PS5 & Xbox Next come out. Also Xbox One S & Xbox One X both play 4K UHD Blu-rays but no one really care.
Next generation is the time to make a move like Nintendo made with the Wii & Switch because not enough people will care about 4K in 2020 the same way the none HD market was still bigger than the HD market in 2006.