The "jelly star" phone looks kind of fun. I just sat in a busy tram and wondered what the scene would look like if we all had phones like that. It's an innteresting thought experiment.
People with headphones looking absentmindedly straight ahead doing their best not to focus on anything, isolating themselves as much as possible to make the complete lack of personal space more bearable.
This is already what crowded subways in my city look like when you pass the threshold where people are too cramped to browse their phones. This is not a bad thing, just a coping mechanism.
I think there is much more room for behavior change if you consider people at a table (coffee or restaurant) with and without phones suitable for continuous media consumption or social network interactions.
I think the biggest difference is actually the lack of newspapers now. Plenty of people were plugged into headphones via iPod/Walkman/whatever was era appropriate. The people who stare at their phones today were staring at newspapers in the pre smartphone era.
So it's only a tiny barrier but if you need it, you turn on wifi sharing and take out the "real" phone. Otherwise it stays unconnected.