We have just revealed some of the leaked screenshots for office 15 and much more news about office 15 is expected to hit the market soon.
Recently in a job post @ Microsoft Careers , it was stated that :
For Office 15 we’re building new products to deliver integration of instant messaging/presence with social networks such as Facebook. In addition, develop Lync XMPP server to deliver seem less interoperation with other XMPP based IM/Presence/Conferencing solutions.
As the Job states , Microsoft is now planning to embed Facebook instant messaging i.e chat feature to office 15 products. The recent screenshots revealed office 15 build 15.0.2703.1000 which is under Milestone 2 stage yet. Screenshots also give an idea that office 15 and Windows 8 might have Metro UI look .