My own personal prediction is that it will be something in the embedded space. Some interesting things are starting to happen there (see: the response to Pebble

My own personal prediction is that it will be something in the embedded space. Some interesting things are starting to happen there (see: the response to Pebble, Arduino, etc). But it is anyone's guess at this point. The people who are working on the next big thing, at this stage, don't even know it yet. These bubbles are born out of people exploring new spaces, with, once a market has been proven, everyone else jumping in to try to take control of that newly discovered space. I think these bubbles are apt to continue so long as new mass-markets for software continue to be discovered, and will continue to pop once a definitive leader for that market has been chosen.