Considering that I'm planning to still update F&H1 a bit after 3 years, it's a difficult thing to estimate when it will be "final". I don't want to make these games forever projects, but there are still numerous things I'd like to add to the game to make it better.
The game is full game in my opinion, as in it tells the story I want and I don't feel like it's too light in content or anything. I do plan to flesh out one of the endings in a bigger fashion and it will probably be the only notable update as far as the canon story goes. Otherwise the updates will be mostly flavour, small details and character backstories. I'd say that half a year is pretty good bet for that ending. I'm also planning to add new playable characters, depending how many of them gets in the game it could take a long while... Sorry for such a vague answer.