Re: There never was meant to be an upgrade path from Nokia
Hard to see what part of the article you're addressing in that comment.
This is not a customer update; it's a developer preview release, and you're expected to understand the risks involved with installing software onto your phone that hasn't been signed off as fit for release. (As you bring up iOS, you might consider what iOS 8.0.1, an allegedly QA'd and released build, did to customer phones: nobody's perfect)
Don't know where you get the idea that there's no upgrade to 10 for Lumia devices: 10 is effectively the same kernel as 8, just with new applications. (Desktop and Phone "Windows" OSes already share a kernel - it was making this change that dead-ended the Windows Phone 7.x series). If the phone has the CPU power to service those new applications, then 10 will go onto the phone. Simple as that.
I would never, ever put a preview OS build onto my primary device, be it a phone or a PC. I've been looking at the desktop 10 builds with a VM, and I'm thinking of buying a SIM-free 6xx to put the 10 builds onto, though, for testing purposes.