My Pop is 73, asked me to help him buy a "tablet" the other day because he wants to keep his sheet music on it. He plays ukulele. I'm a dyed in the wool linux and android user, he's an old mainframe engineer from the 70's. He's not unintelligent but has had a bit of a decline in mental acuity so after much soul wrangling I steered him towards an iPad. He loves it. Simple, "intuitive" ( for him ) just his speed. He immediately downloaded "Onsong" after I helped him research it and off he went, merrily importing chords and music.
Here's the observation- if regular users / geeks abandon Apple for unwalled gardens, it won't be readily apparent because there are always going to be older people like my Pop buying Apple products for the ease of use and simplicity. Just like there's always gonna be an older AOL user out there. But there may be no serious revenue stream in it for Apple. Older people use devices differently than most of us.
See, my pop is not interested in any more apps. He's found the one thing he wants to use an iPad for and he's DONE. I showed him how to read his gmail on it on the web, he flat refuses to read a book on it, doesn't care about buying music ( he prefers to listen to ukulele examples on youtube) doesn't play games, doesn't care about facebook, twitter, instagram or anything else. He uses his laptop for his finances... he even wants to unlink his credit card from the appstore so "hackers" won't steal his card number.
So Apple managed to sell him an iPad and *one* app. I can guarantee you he will use that one app and be perfectly content till the battery stops charging.