Saves are stored in "/game/saves" folder (in Renpy games). One can manually copy that folder into newly instaled update, to be sure. Or just install new update, start game, and it should be auto-copied, and after that remove old version. Also (not rly sure) they say, even when game was deleted, saves will reappear in a new instalation, but this is kinda bad news, as there is some data storage beyond our basic control. Probly hidden in some backup system folder.