I doubt development will take as long as in the past because with Witcher 2 & 3 and Cyberpunk they also had to develop a game engine in parallel with the game itself and that takes as many or more man hours. Pre-development used to include making a game engine before you could even start development, now pre-development means a one time having to learn a new game engine that's already finished and stable. Also during the development of Cyberpunk they had to convert there DX11 game engine to DX12 which likely held up game development itself by months even over a year just waiting for the newer game engine to actually be useable. Now if Microsoft comes out with a new DX13 it's up to Epic to do the conversions and I doubt there will be as big of a version change as we saw with DX11 to DX12 which are radically different at the core level (shader pipelines, CPU, GPU and memory handling, etc.)