Here's one report on iPad relevance and model use:
"Most iPad owners are using outdated devices, and that's a disturbing trend for Apple
More people use the iPad 2 than any other iPad, according to a study by market research film, Localytics, shared by AppleInsider.
The study collected data from over 50 million iPads, and over 20% of those were the iPad 2, which was released way back in March 2011.
The second most used iPad is the iPad mini, which was released in late 2012.
To compare, only 9% of iPad owners in the study use the latest iPad Air 2 that was released in 2014, and 0.3% use the latest iPad mini 4, which came out this year."
http://www.techinsider.io/apple-ipad-2-is-most-used-ipad-2015-11
"Most iPad owners are using outdated devices, and that's a disturbing trend for Apple
More people use the iPad 2 than any other iPad, according to a study by market research film, Localytics, shared by AppleInsider.
The study collected data from over 50 million iPads, and over 20% of those were the iPad 2, which was released way back in March 2011.
The second most used iPad is the iPad mini, which was released in late 2012.
To compare, only 9% of iPad owners in the study use the latest iPad Air 2 that was released in 2014, and 0.3% use the latest iPad mini 4, which came out this year."
http://www.techinsider.io/apple-ipad-2-is-most-used-ipad-2015-11