Just to confirm what's been stated already. As a general rule, whenever we make changes to the map, we recommend starting a new game to avoid potentially weird stuff from happening.
Otherwise, saves will work if you update to 2.8. But if you are running a game you are super invested in and want to finish it, it is highly recommended to use the beta branch and opt into 2.7.2 once it is made available. That way, you can still earn any achievements you may want to go for without risking the save from breaking due to changes/new features.
Otherwise, saves will work if you update to 2.8. But if you are running a game you are super invested in and want to finish it, it is highly recommended to use the beta branch and opt into 2.7.2 once it is made available. That way, you can still earn any achievements you may want to go for without risking the save from breaking due to changes/new features.