Karl Soulé offers up 4K presets for Adobe Media Encoder, writing, "I was asked the other day when Adobe will offer a 4k output from the H.264 encoder. The answer is simple – it’s there today! Currently, the Media Encoder (and, by association, Premiere Pro) doesn’t ship with presets for 4k H.264 output, simply because it’s not a common enough format. But it’s reasonably simple to make your own."
Read more and get his presets here on his Adobe blog.