Yes, it looks like Google is moving on from OpenID 2.0 to OpenID Connect, which is the new standard [0]. It appears that OpenID 2.0 login will be kept for compatibility, though [1].

Google+ Sign-In is an implementation of OpenID Connect, with some nice features built on top:

"Google+ Sign-In is built on the OAuth 2.0 and OpenID Connect protocols. It supports over-the-air installs, social features, and a sign-in widget on top of standardized OpenID Connect sign-in flows. Google+ Sign-In works for all users with a Google account, whether or not they have upgraded to Google+." [2]

[0]: http://openid.net/connect/

[1]: https://developers.google.com/+/api/auth-migration

[2]: https://developers.google.com/accounts/docs/OAuth2Login