I cannot help but feel like this is a step on the eventual phasing-out of Google's most recent attempt at a standalone social network, Google+. Until just recently, the company was doing all that they could to force it into each of their services; now, they give you a "no thanks" option when creating a Google account (for GMail, Google Docs, and so forth).
Image Credit: Marketing Land
Marketing Land claims to disagree. They expect that Google will "continue making subtle changes to the service" such as enhancements to Hangouts and Hangouts on Air, or even spinning out Google+ Photos. The thing is, these initiatives will not mean that they are supporting Google+; rather, it says that they are supporting the parts of it that worked. The article did not even mention actual Google+, the social network, as something that Google might consider updating — just Hangouts and other sub-products.
This all depends on what you consider "Google" to be. Not having a profile on a message-sharing service does not really change much, despite how it feels. The real point should be reducing the barrier-to-entry for cross-promotion. A unified login helps in reducing effort to acquire new users without any real risk. Forcing users into your ecosystem could help, if it does not shove them away.
And Google seems to care even less about keeping users in their eco-system with a limited communication and microblogging platform.