

Then you’ll play the DLC with the updated graphics etc. There’s nothing mystical about the upgrade pack - it’s just engine optimizations to let the game run natively on new hardware, probably some revamped textures, etc. The base game has been DLC-aware since the DLC was released. Having the DLC doesn’t change the game code, it just makes the extra content accessible.
There was supposed to be a sequel but a whole bunch of fuckery kept it from happening.
https://en.wikipedia.org/wiki/Eternal_Darkness#Cancelled_sequel
Followed by Dyack forming another studio, botching three crowdfunding attempts, forming another studio, then shuttering the project.
It really was a mess.