I wish it had 8K support, given Japan is actually already planning on starting broadcast trials for 8K in roughly two years: http://www.futureleap.com/2013/03/japan-plans-8k-broadcasts-...
We all know 4K is next, we know that clearly there'll be something afterwards, it would be good if the next hardware we buy planned for that.
Thunderbolt, BTW, has similar limits: http://superuser.com/questions/441395/what-is-the-maximum-re...
"Yeah, this hardware will cost more, but it has to support a bandwidth level that won't be in use anywhere in the world in the next two years."
Seems totally reasonable to have a version in step with the emerging generation, rather than future experiments.
The current MBP retina display, if used on a 27 inch monitor, is more than 4K.
Conveniently, however, it's less than 8K - as is a 32 inch retina monitor.