What's the alternative? I doubt even someone as big as Samsung will be willing or able to develop their own alternative OS (atleast one that can actually grab marketshare enough that critical apps get ported), and I can't imagine them wanting to hitch their wagon to the Linux alternatives.

> Not sure if the big manufacturers would want to depend on a proprietary Google OS.

They already do; Google's flavour of Android adds plenty of proprietary components on top of AOSP.

"Not sure if the big manufacturers"

thats the thing, they would supply android os to these major manufacturer, but for the rest??? need vetted applications