I watched Unbox Therapy's smartphone in your pocket video today. I thought about it and realized it's probably just iMessages for me. I think that's the big reason why Apple won't open it out to other platforms.
Other than that, I think I could leave the ecosystem. I don't really use iCloud. I don't mind Android, it's gotten a lot better since its early days and the UI is solid now. I actually like Google's suite, including Google Maps. I also don't mind Windows 10. Maybe I'm not a power user, but for the most part I find it to be just as good as OSX High Sierra.
So I was wondering why you're staying in the ecosystem and what would it take for you to leave it?