On December 8, 2014 there was a blog post on the Vimeo staff blog titled Oh hey, 4K — download ultra-HD videos. In this post they state that 4K videos can be uploaded to their site (which has been the case for a while) and now they can also be downloaded by Vimeo users.
They end their post by stating: “And while we don’t yet offer 4K streaming on our site, we’ll be ready by the time broadband providers start widely supporting the high speeds required.”
Interestingly, Philip Bloom notices that 4K streaming has been snuck in and at least a partial implementation exists. See Philip’s blog post titled Vimeo sneaks in 4K streaming. Hooray!.
Vimeo has hinted in the past that implementing 4K features on their site is on their radar and one of their top priorities and now it appears closer than ever.