Mods are what kept the Elder Scrolls games alive for years. People are still buying Morrowind today and playing it for the first time, or replacing their long-lost disks to relive the great adventure in a new, shiny modded form. Luckily, they don't have to pay for any mods but Skyrim so far. But think ahead: Fallout 4 will certainly release with full Steam Workshop support, including monetization. It won't be "such an old game" unworthy of modding on its launch day, will it?