Yammer will be Integrated With Office 365, and we have only seen the begining in Our Office 365 Navigation bar.
First step was giving the Office 365 Navigation bar a shortcut to Yammer.
Second step is giving SharePoint Online and OneDrive for Business Yammer discussion Integration. Discuss documents and sites.
Third step is announced now and will make Office 365 Users seamless navigation between Yammer and Office 365. But the Yammer Service will still be a service outside the Office 365 tenant. This step federates Yammer with Azure Active Directory.
Fourth and last step will be moving Yammer Enterprise into the Office 365 tenant.
Who will get it?
Rollout is scheduled between December 2014 and March 2015. We will need to activate the feature in Our Office 365 Admin Center, and break Yammer SSO if it’s enabled.
Yammer must also be selected as default Social Network, to make the navigation seamless.
Source: Yammer blog.