About adding updates to a released Twine game

I am planning on releasing an rpg game that will have future versions down the road (for adding new quests, etc.). Will this be possible without breaking the previous saved games as long as I don't edit the already existing variables? Is there a way to perhaps add a new StoryInit passage as a sort of append to the original StoryInit? (e.g. a StoryInit for a Chapter 2 while the original StoryInit is Chapter 1) to make sure I don't edit anything that could ruin the saved games?

Thank you so very much! (I'm using Twine 2 and Sugarcube 2's most recent versions)