I think that wearable computing will be the next big thing and it will take off even faster than the cellphone did (which itself was one of the fastest adopted technologies in history).
It will happen because people permanently plugged in to the Internet will simply be smarter than people who aren't. Imagine wearing your Google Glass, and it's microphone is picking up keywords from conversations around you and automatically Googling them in the corner of your eye. If you have an automatic encyclopaedia and other's don't, that's potentially a big advantage. It would sure make it hard for a salesman to pull one over on you, with all the facts and figures popping up in your glasses as they talk.
And people will discover if you say a certain word you get a funny search result, and everyone in the conversation that has Glass (or Apple's version) will be laughing together at this silly thing that just popped up, and people who aren't "connected" will feel left out. Pretty soon everyone will just have to have one.
This is a nice fantasy, but this kind of thing isn't made possible by the presence of a HUD on your head, it's made possible by Artificial Intelligence which actually hasn't developed to the stage that it can actually do this stuff yet.
Google glass will be able to do pop-ups and pop-overs on what you are seeing, but the pop-ups will be more like advertisements for coupons and restaurants. It will be able to link into social media eventually like foursquare ratings on restaurants etc. but it won't be able to do anything or give you any information that pulling an iPhone out of your pocket can't also give you.
What you're thinking is that there will be some magic (Artificial Intelligence again), computer entity behind it all that understands you, understands what you want, what you think, knows about all your friends and interests and can talk back to you and suggest things in real time. This is the basic fantasy piece built into every single "concept" of future living you've ever heard about since they first started talking about "the future" at all.
It will only happen when Artificial Intelligence becomes a reality. So far, there is absolutely no indication at all that the basic problems of making an artificial intelligence have been solved or even correctly understood to the point where they *may* in the future be solved. This kind of thing (a computer that can understand you when you talk to it), is either impossible, or is literally hundreds of years out. Siri is pretty much the pinnacle of what we can expect from systems like this for the foreseeable future. The accuracy will be improved, but it won't gain magical sentience overnight.
It won't happen in your lifetime that you will have such an "intelligent assistant." Get used to it.