Oh gawd, don't call it 'Until Dawn' 2. Hopefully this is just what we're calling it until something solidifies, because....
The story could continue without calling it Until Dawn...2.
Unless we're going to see more of Hannah in the sequel - there's nothing in the game that warrants such a naming convention.
And even considering a premise that involves everyone who survived - and even if Supermassive is taking notes from games like Mass Effect with previously saved game data, enumerating games instead of naming games just seems a bit inadequate, and lazy...just saying
Until Dawn : [
put subtitle here]