I don't think that most enthisiasts, semi-pros, or pros are going to sit on a camera body for ten years. I think your average consumer tends to churn through cameras at a pretty fast rate as well, although there are certainly some who stick with what they've got as long as they can to get the most for their money.
The vast majority of dSLR purchasers never buy another one. Only pros and genuine enthusiasts do. Of all the people I know that have dSLRs, almost all of them still use the first one they ever bought. I'll provide a list of people I know, aside from me - 10D, D70, 5DII, Rebel XT, 300D, T2i, T4i. In fact, of everyone I know, only one person aside from me has ever "upgraded" and that was to move from Canon (40D) to Nikon (D200 - still using that one). And my upgrade was from 10D to 5D when the 5D first came out.
This next path (looking like 20D+5D to 7D2+6D) will be my first body upgrade since 2005. I've cycled through a great many lens changes since my first DSLR purchase (17-40L, 28-135IS, 75-300IS, 50/1.8, 50/1.4, 35/2, 35/1.4L, Sigma 20/1.8, Sigma 15mm fisheye, 100/2, 85/1.8, 24-105L, 70-200/2.8L IS, 70-200/2.8L IS II, Tamron 1.4x, Tamron 2x, Kenko Pro 1.4x, Canon 1.4x II Canon 2x III, Meade ETX-125PE, Celestron Edge HD 11).
I'm with Jrista on this one based on my experience and living in Japan where buying a new camera every 6 months seems to be the norm. My 5D2 feels very outdated amongst the multitude of 6D and 5D3's out there (some of them are definitely not pro). Perhaps in the past people held on to their gear for longer but (mainly thanks to Sony) things are changing rapidly so naturally folk want to keep up. I can't imagine keeping my 5D2 (which I bought 2 years ago) for any longer than another year, simply because by then it will be really hard to sell.
Also camera's have come down in price considerably so it's easier to justify a new purchase. I went through 3 bodies in 4 years, not even including my EOS M. And I consider that conservative. It's like PCs and laptops now. Who keeps a laptop for 10 years? Yeah it works but why burden yourself with slow ass gear when you can buy the latest for a few hundred bucks?
My longest kept electronic device is a hi-fi that my dad bought me about 20 years ago. Still works (but the speakers gave way ages ago). I only kept it for sentimental reasons. The thing is giant and a first generation iPod could easily outperform it! So in that respect I get why someone might keep a camera for ages.