Not full integration between Skype for Business and Yammer, but you can now use Skype for Business while you are in Yammer. Instant Messaging and Presence only as the web app version doesn’t have audio and video.
SfB presence is also integrated into the contact card in Yammer and there is a “call with Skype” button that launches the desktop SfB client.
it’s not integrated in that it doesn’t displace Yammer direct messaging or show presence/links on Yammer contact cards. Hopefully we will see deeper integration in the future.