If you have a modded game directory, as in vehicles, weapons, sounds, etc, LSPDFR/Rage working is the least of it. The worst part about modding is that all your modded game files, specifically the ones I just mentioned, will always cease to work with GTA updates. Rage will stop working, but only because it needs to be updated (and possibly ScriptHookV, sometimes). That is more of a waiting game on your part for the update to be released.
After the update, you'll just have to re-add your stuff manually.