Google has dropped the Google Plus link from Gmail and other Google services such as Youtube, Google docs, etc for the logged-in users.
Google has remove (+)sign before the name of the logged in users in Google. And the hyperlink to the Google plus is no longer exist.
But you can login through Grid Menu.
Last week Google Plus Executive Bradley Horowitz launched Collections Feature in Google plus.
Bradley Horowitz says No, Google Plus is not dead. In fact it's got more signs of life than it's had in some time.