Recently Google has announced that they are going to introduce their Google+ hangout in Gmail too. Google has announced new hangout app for iOS and Android along with new extension for Chrome.
If you recently login to your Gmail account then you had found that Google has updated your chat to Hangout, if you are not liking new Hangout then you can revert back to older Gmail chat.
Just login to your account and then you will find a small arrow just next to your name, click on it and then you will find an option to Revert Back To Old Chat.
We don’t know whether this option is permanently or temporary but we think its temporary and Google soon remove it.