There're a few questions I got from watching the stream, and the FAQ didn't really cover it. Will the Steam TSW5 for existing TSW4 users be a separate install or it will upgrade/install on top of the existing TSW4 install? And if it's gonna be separate, will there be a way to transfer one's progress from TSW4 to TSW5? One of the reasons I'm asking is because I was planning to upgrade one of my storage and move the install and I'm planning on how to do that.
Train Sim World 5 is a new game. It will require a separate installation and redownload of any add-ons you may be entitled to. You find more information on profile transfer in the Train Sim World 5 FAQ.