There doesn't seem much of a trend in that direction. Most city office jobs could be done remotely but there are advantages to being central. You can meet people, go to conferences, chat over coffee and the like. It's kind of ironic in a way - you might have thought being able to work form a laptop would lead to people spreading out but it seems to lead more to people thinking they may as well bring the laptop to a cafe or office in central SF, London, NYC or the like.