Seriously, the amount of jokes about the iPad when that first came out were hilarious because now all those jokers have an iPad themselves.
Sales have dropped off, but even the browser market share for iPad remains high among tablets.
Most of my travels are in Canada however, and in Vancouver , Calgary, or Toronto the ratio is inverted - more iPads than laptops. Business meetings too - lots of iPads.
I know my 5 year old prefers our iPad to any other device or toy - even the big screen projector. This is similar with other parents in our circles where iPad grounding is one of the more effective forms of discipline.
These are all anecdotes and in the grand scheme mean little, just a counter example to the "collecting dust" theory. They're also still outselling all Macs by 3x though it used to be 5x. So something is happening to iPad purchase trends but it's not clear why.
If you are talking about the entire table market dropping in usage then it isn't significant (6% y/y): http://www.idc.com/getdoc.jsp?containerId=prUS25593415
Without the subsidy of mobile phones people don't seem to buy new ones as fast. Doesn't mean the iPad is dying, just that the market is closer to saturated than it was 2 years ago.
Even if you have the iPad 2 for instance, it's a very capable device, there's no reason to go out right now and buy the latest iPad unless you specifically want extra features like Touch ID.