Is it? Maybe the iPad is supplanting laptops in some niches, but I'd argue that those are ones were maybe a laptop wasn't the proper device in the first place.
AIUI Glass can't do augmented reality only because the API is currently too restrictive, which is really too bad. Using a HUD as a glorified head-mounted camera seems like a huge waste of opportunity. Even if they never open up the API, a HUD can still do things that a watch is going to struggle to replicate.
This[1] is a good overview of what it takes to make an AR device, and it examines the Glass hardware in respect to that. The verdict? The hardware is there (although it's not stereoscopic) but the software is behind. You have to start somewhere, though.
[1]: http://blog.integratedrealities.com/?p=261