I'd say it might be possible in a future expansion if we're lucky (if sales justify it and it is practical to implement). Personally, I am not getting my hopes up though as I suspect Larian discovered that a highly reactive day-night cycle really needs to be designed into a cRPG from the ground up (taking into account housing for npcs, quest design, NPC scripting, etc), rather than added at a point years into development. It's probably possible to vastly alter the game to force it in there, but it obviously proved impractical for Larian to do so. I have greater hopes that their next game will include it, and be even bigger and better than D:OS.
However, from that Twitch stream introducing the editor we learnt that it is easy for modders to add some cosmetic day/night/atmospheric changes and effects based on trigger points. So I wouldn't be surprised if some enterprising modder(s) came up with some innovative cosmetic day/night effects mod(s) for D:OS, even if it won't have the extensive reactivity that would require a large team to create.
