I spent some of BUILD trying to nudge rumors out of folks. I wasn't successful, but I tried, because I care and because I was one of the few people left with a 950 in my pocket.
Most employees I talked to about it had already fallen into switching to Android, but there were some near tears about it. The only "official" Microsoft answer about it I got (from multiple people, so it sounded like a "Party line" and thus why it felt "official") was that "Microsoft was just too late to the market".
A lot of slides still had phone-sized devices on them, though admittedly some of that was probably just graphics reuse from previous years. Fluent Design documents all still reference phone-sized and phablet-sized devices (and even Band-sized devices).
I enjoy chasing all the rumors on CShell progress, as that does sound like a key to future mobile support. (The one time I think I got close to a wink/nod sort of thing about it at BUILD was when I responded to that "too late" party line with "Or was it just too early for Windows 10 on mobile? CShell was expected to be developed faster than it has turned out to be, hasn't it?".)
I know a lot of people seem to be enchanted with Surface Phone rumors, especially the recent "Courier" folding/multi-screen concepts we've seen from Patent applications.
Personally, I've been excited about "HoloPhone" rumors, some of which I believe I started accidentally by connecting obvious dots, and just hear come back to me through the telephone process of rumor mills. Alex Kipman of Kinect/HoloLens is rumored to be the owner of whatever the next mobile/handheld computing device project is, so I certainly expect some Mixed Reality/Holograms fun.
Anyway, nothing but rumors and hope, but as someone that's been on the platform forever (my last non-Windows phone/handheld computer was an iPhone 3GS, a million years ago), I want to believe, as crazy as that is getting to sound.