Unfortunately as it stands now, yes you will have to redownload the game when 1.3 comes but due to how Ren'Py stores saves your save file will transfer to the new version and once you open, load and re-save in 1.3 you can safely delete 1.2 if you want to save space. The only Koikatsu/Ren'Py game (the art and playstyle of this game) that has an updater right now is Champion of Realms and even that updater is still in testing and is far from good atm. Luckily this and most other Koikatsu/Ren'Py games usually have substantial updates that add close to 2 or 3 hours of gameplay per update for their free releases here in Itch, every month or so for some. HHG is one that takes a long time to get the free updates but they are BIG when they come.