I do not agree that the way to go is BB10. As I said, BB10 is in no way built for the modern world! It worked on feature phones. It worked on BlackBerry's! It does not work on smartphones. BlackBerry has gone the way of Android because finally they realize this. Maybe with their high quality hardware and security running Android they have a chance to be a manufacturer but BlackBerry as an operating system is hanging by a thread and with the way the market is going it won't last long. BB10 isn't fluid enough, and by that I mean it doesn't change enough.
Microsoft is invested in Windows 10 Mobile and there's no way they're giving up yet. Universal Apps, Continuum, all new core apps, a new camera, an entirely new operating system, Windows Design Language, everything is there. It's not a two-horse race. There's a lot of horses there, just all but three are so far back in the distance you can't even see them. Windows Phone is right there and Microsoft is pumping so much energy into it that as long as they don't stumble they have a chance of being a contender again. If Microsoft worked with BlackBerry to use some of their ideas, get that infamous security and maybe a hand on the BlackBerry Hub, that would be great. But Microsoft doesn't need it, and it may actually weaken them.
The worst thing Microsoft can do is spend their precious funds on acquiring BlackBerry as a whole. That would be a foolhardy decision. Acquiring Nokia was likely a mistake but Nadella at least rolled with it and is using it to his full advantage. Nothing can be gained from buying a dying company that's sinking the last of its energy into Android, Microsoft's mobile competitor.