Gilly from MyMicrosoftLife has discovered that the new Wave 4 header is currently accessible if you visit https://consent.live.com and sign in with your Windows Live id.
The navigation of the links is working completely fine but all the links are pointing towards Wave 3 services. The Office link redirects to https://www.officelive.com and currently it’s not possible to create new documents from the hover menu.
The Messenger menu on the top shows the number of online friends and by clicking on any friend you can start a conversation as shown above. The new Web Messenger appears at the bottom –right (like Facebook and Google Chat) of the page and some would say it looks like the Google’s Web messenger. But its looks better than that.
Visit https://consent.live.com and experience the new Wave 4 header yourself.