I was under the impression that this was a bandwidth issue for the HDMI port, so I'm curious to see how a kernel extension would get around this issue.
I came across this while looking to see if I could buy a 4k display for my 12" Macbook (2nd gen.). My brief reading of it implied that it would be possible to drive it at 60hz. but maybe you are correct.
Looks like it might require an extra graphics card, or something like that? I haven't looked into it in detail, but it doesn't look like this thing works on a MacBook.