Microsoft initially announced this feature on the Lync Conference early this year. Last Friday, on 5th December, Skype 7.0 has been released and with this version, video calls to Lync are possible. Be aware that an update for Android or iOS Skype App will follow in the next weeks.
So what is still missing in the Lync-Skype Connection?
– Only Peer2Peer Calls are possible. You cannot add a Skype contact to an existing conversation. You cannot schedule a meeting with two Skype contacts. I am not sure this will change with Skype4Business next year.
– You cannot search for Skype Contacts within your Lync Client. You still need to know Skype address and you have to add the contact using a specific menu entry in Lync. Details here: https://products.office.com/en-us/lync/lync-skype-connectivity
– Skype user must link his account to a Microsoft account (aka Windows Live ID)