Google has quite a few messaging platforms and they barely talk to each other, if at all. They have Gtalk, Google+ Messenger, Google Voice, Chat for Drive, Hangouts, and even the SMS application, which others have integrated into their messengers a long time ago. Of all of these, only Gtalk and the G+ Messenger can talk to each other, but even that is not perfectly integrated.
A unified messenger that integrates all these messaging platforms has been requested from Google for a long time, and with Android 5.0 they might finally deliver. We've seen some unified messenger code inside a future version of Chrome OS before, and now a new rumor says that this new project, which should also come to Android, is being called "Babble".
I don't like the name Babble itself too much, as I don't think it's a name that could get mainstream that quickly, especially in non-English countries, which is why I hope this is only a code name, and the actual name will be something different. I do like the icon though, which seems to suggest there will be at least 4 different messaging platforms being integrated, and I hope one of them is the SMS platform. It's very necessary to integrate that into this app, too.
Apple has done it, and there's no reason for Google not to do it either, even if that ends up making the carriers furious. But Google needs to stop being okay with the fact that whatever makes the carriers angry, Apple gets to do it 2-3 years before they even ramp up the courage to do it. Google needs to be a lot more pro-active with things that could disrupt the carriers. They have the majority of market share in the smartphone market. They need to start acting like it, and not like they have to do the carriers' bidding all the time.
It's why I'm hoping video-calls and VOIP calls get a lot more integrated into the dialer in Android 5.0 and beyond, so people get used to using voice/video over the Internet, instead of Voice, and therefore completely bypass the carriers, and be able to talk to anyone in the world regardless of the "network" they are in, and for the same price every time.
The deep integration of the messaging platforms and VOIP/Hangouts are two of the things I'm expecting most from Google I/O and Android 5.0 this year.