Seems like it will be quite possible with Glass to ditch the full phone and go with a mobile hotspot. By doing calls over that we can push the carriers into what they should be (according to so many geeks these days), dumb pipes.
Heck, keep the hotspot in a bag or make a wearable, unobtrusive hotspot belt or anklet, then the battery size & life can be increased while still having no gadgets in one's pockets. One could put a widrive on the belt/anklet too, so Glass becomes useful even without constant access to the cloud.
...at least until the technology becomes small enough. Though I'm not sure it would be good to keep a GPS/GSM/3G/LTE antenna blaring next to your skull the whole day.
