I can't guess how long that will be, as I think in the worst case he could upload the game to Steam and then stop developing the game.
Best case scenario, I'm guessing he's already hired the Steam team and started working on it, adding a month or two to the typical upload period of 3 months.
However, as stated in the schedule, he won't start any additional work until he uploads Christine's party event, and after uploading Christine's party event, he will take a 2-3 week vacation before starting to look for staff, and after finding the staff, he will start working on Steam. I'm thinking it's very likely.
So it could be six months or it could be a year, I don't know.