Re: They already have
They may continue to use AOSP, but it would take a phenomenal investment by someone to keep it anything like up to date. If Google remove themselves from the community there'd be an almighty development vacuum to be filled.
And I can't see the like of Samsung, etc stumping up the man hours. They don't have swathes of highly talented OS developers sitting around just in case. It's a vacuum that might not get filled.
If a bunch of manufactures suddenly find themselves needing an OS, they could do worse than BB10. There's some good aspects:
1) it'll play with cars nicely. QNX is beginning to rule that market, and there'd be a lot in common between a BB10 phone and a QNX car
2) technically, under the hood, BB10 is very good
3) BlackBerry are almost certainly willing to license on favourable terms, and indeed are very purchasable.
4) whilst it isn't quite so flush with services as Google, there's a lot already there
5) it's Android runtime provides an app bridge
6) it doesn't data slurp
If all the likes of Samsung, HTC, Sony, Huawei, etc all decided to standardise on BB10, that'd save BlackBerry and there'd be an instant market for apps. That would make it viable for developers to write for it.
Though what I suspect will happen is that Samsung will try to do their own thing, fail, whilst everyone else whither and dies rather quicker.
Like him or loathe him, Jobs was right about one thing; software matters. The android crowd may find themselves with any software pretty quickly unless they take matters into their own hands.