I'm also hoping self driving cars will let people choose more appropriately sized vehicles and perhaps untether luggage from human transport (reducing the vehicle size even more).
You're not going to get around congestion, but I think we can break the norms of 9-5 sitting at your desk office hours. White collar jobs have changed dramatically in the past 40 years due to other forces; offices to cubicles to "open floor plans." But we've stuck to 9-5 and people expect me at my desk.
If broadband internet, or high speed data for train commuters, hasn't made working remotely a thing yet, then I don't see how self-driving cars are going to do it. Seems more likely to be the opposite, like the Googlebus: look how much easier it just got for you to work even more hours!
I'm not sure what the saturation for people taking commuter trains is, but if autonomous cars get adopted en masse, that might be the difference? One thing I didn't consider before talking to people in London, when the subway is full there is no relaxing and reading a book. You're elbow to elbow and likely standing the whole time. I know commuter trains aren't like that, though.
Like you're saying, googlebus makes it easier to work longer hours. Conversely, carpooling (or missing the train) keeps people to sane working hours. Taking a bike pushes people to leave before it gets dark outside. I'll be interesting to see how it changes our behaviors.