Well, the thing is that in one of my modpacks I wanted to include some maps I created, so I put the maps in the Overrides/saves folder. But... When users of the modpack download the new version; Will they worlds be deleted? Thanks
Someone correct me if I'm wrong but I'm near positive it acts like "copy and paste" while merging similar files. So if they don't have progress on the same map that's included in your modpack, then it shouldn't cause any issues.