It's entirely possible that somebody will call you into an office and tell you that you're not a team player. It's possible that they'll explain how it's crunch time and everybody's pulling together and it's unfair to the other people on the team if you don't pull too and how you're letting everybody down.
That's fine.
It's also possible that after telling you these things enough times and writing them down, they'll fire you.
That's fine too.
There are worse things in this world than being a talented developer on the job market in the Bay Area. If your company is silly enough to fire you for working the hours you agreed to work when they hired you, that's a shame. But you'll probably find yourself with a better job a week later.
More likely, though, you'll find that they deal with it. Better still, you might be able to convince a few of your co-workers to also make life a priority. Who knows, six months from now you might have an entire office full of people working sane hours. It's definitely worth a shot.