I am still going to do my Adobe stuff on a colour corrected monitor or a set of those and not on something less than 13 inches diameter to be honest.
On top of that, external monitors are only mirroring the internal display hence equally useless for palettes and second screen applications.
I rarely do any work for print these days. If ipad does finally run full design and video production apps one day i will definitely need it to be able to easily connect to a larger monitor or two.