[Technology] Google Hangouts: no more XMPP, but yes to SMS

So, I'm disappointed to hear that Hangouts will replace Talk and not support XMPP.  I wonder whether there's a technical discussion available as to why.  I'm glad to see it support SMS.  Does iMessage already do that too?  I think BBM does.  Who knows.  I just want an end to running multiple redundant platforms.