Adopt an standardized OS would push manufacturers out of business.
They don't want to be recognized as another android phone, because then consumers would simply move tho the cheapest capable ( or faster, or better camera) android phone.
My thought is that Samsung need that it's phones be seen as a totally ( and worth) product that Moto X. So they can monetize on this perceived value.
At least we still have Linux and Mozilla (and Canonical), so I still think more open mobile/tablet/phone platforms are comming. They might run Android apps -- or might not. They might be able to work with a workable for-profit/pay marketplace/app-store (AFAIK the only working such market place for open OS' is Steam -- maybe Valve will eat everyone's lunch in the end. Steam for mobile apps and games? Why not.).
Hangout exemplifies everything that is bad with the path Google is on. It replaces a system based on open standards, that (mostly, except for federation?) welcomed any and all existing clients -- and a system that allowed for having separate apps for handling IM and SMS (say, maybe you wanted your IM to alwasy use OTR, but not for SMS).
The sad thing is, contrary to what Google claims, I don't think publishing a Google app that did most things would have been untenable while basing the work off of existing standards. I think it would probably have been easier.