For the most part you answered your own question. Rewriting an engine for DX12 isn't something you can do in between game releases. UE4/Epic has been working on it since October 2014 (the first DX12 build was released, they've probably been working on it before that) and still doesn't have it fully rolled into their latest release. For the second part, what's the point? Like you say manufacturers are pushing 4K, but it still has below 5% market saturation. And Multi-GPU setups are also rare. Does Avalanche really going to spend 50-60M rushing DX12 adoption for the handful of users it would actually effect? Like most of these people are buying the game already. There is maybe like less than a hundred people with SLI/Xfire/4K that would actually buy the game specifically for those features. 4K adoption has to come from monitor manufacturers making it worth it. Multi-GPU has to come from Nvidia/AMD pushing it to devs and making it easier to develop for (something AMD has been heavily focused on).