My home desktop is a 2009 Mac Pro. I also have a personally owned 2008 Mac Pro that I keep at work. They are both too old now for the new version of OS X, so it looks like they will stay on El Capitan.
At some point, I'll either need something that requires an OS later than El Capitan, or the hardware will die. At that time, I would not be surprised if I moved to something else. A lot will depend on what Apple's desktop lineup is like when the time comes.
I would want to be able to move the SSDs from my current Mac Pros to the new machine(s), and nothing in the current Apple desktop line seems designed to make that easy. I would be reluctant to buy any of the current Mac desktops with the Apple upgrade to SSD because that raises the price too much.
The iMacs are also problematic because of the built-in monitor. I don't want to have to keep a separate monitor for my Windows gaming PC, so prefer a Mac desktop without a monitor so that the Mac and PC can share it. For a while iMacs had a feature where they could be used as a monitor for another computer, but I believe Apple dropped support for that.
I suppose I could use an iMac and use Bootcamp to boot an external disk with Windows for gaming, but I'm also not sure about the iMac from a gaming performance point of view.
Another piece of Apple hardware that may be endangered soon for me is my iPad. I've got a 3rd generation. Like my desktops, it is now too old for the current OS. (And even the last version of iOS Apple released for it had some of its most touted features disabled on iPads as old as mine).
I'm seriously thinking of something in the Surface line when it is time to replace the iPad. That's because I'm getting annoyed at the multitasking performance of the iPad, particular of the browser. I'm tired of being on some big page, like a heavily commented Reddit thread, switching to another app or another tab within Safari, then switching back and having the browser have to reload the page. This is especially annoying if I was writing a comment and switched away to get some information I needed for the comment. I end up having to select-all/copy what I'm working on before switching away, so I can restore it if the page reloads, but then I cannot use copy/paste to copy in whatever it was I switched away to look for!
I believe that Surface is running more of a desktop OS with tablet enhancements than a separate mobile OS like iPad uses, and so I'm hoping that it would multitask more like a desktop system does...and so switching between browser tabs, or between the browser and another app, would not cause browser page reloads. I've yet to look into this in detail, though, to verify this.
My iPhone is great. I see no reason at all to consider switching to something else in the phone department. It's just tablets and desktops where I foresee problems.