This is why I cast games as regularly as possible
[*], and also why I put the game version used in the description of each cast. I realize not everyone reads those descriptions, but it's the best I can do (short of including it in the video, which seems excessive) to ensure people watching the game know enough details to know whether to expect the game they are playing to be the same as the one they are watching. Also, by making new ones regularly, it ensures that there are at least a few videos that are reflective of the most recent changes, and that those videos are most visible to someone finding the channel, or searching for Zero-K videos from the past week or month.
I also doubt that a global rename (especially if it is the last one) will hurt the applicability of casts any more than the various mechanical and UI changes that have happened over the course of my ZK casts. The game is quite different in many visible ways since July 2013, so people watching old casts are watching an old, out-of-date game. This is the same with most games nowadays that have regular updates. Stuff changes, and that means old casts of basically any game need to tell the viewer what version of the game is used, since those casts will likely be obsoleted by updates to the game being casted. Whether that's a good thing or not is a different, and industry-wide, debate, but it's a thing that's been normalized one way or the other.