[...] for me the ability to buy a single copy of a game and share it between all ~5 xbox users I know will be a lot more useful.
My guess is you're reading too much into that feature, that won't be how it is going to work. No more than one person will be able to play a shared game at any given moment, so no multiplayer co-op or combat, and no achievements for anyone but the owner, scrap that, the licensee, plus a lot more of similarly arbitrary restrictions.
Not so much of a dilemma. They could adopt Android, and port their own apps to it. In exchange, it will mean they'll have access to, not just the Android on their hardware, but Android phones all over the world, a market hundreds of times bigger. This way, they can make their own hardware and software, two sources of money, which they can bundle for a reduced cost and rejuvenate the BlackBerry brand.
This. They could even make it go both ways, still release dedicated Blackberry phones, running latest Android versions plus their own UI on top of that. Have their own phones run premium versions of their apps, and sell basic versions on Google Play that run on all Android devices. Call it Business Android, or whatever.
the magic of those extra 0.85 inches.
That's what she said!
Of course you can't flap your arms and fly to the moon. After a while you'd run out of air to push against.