I think the major problem with diplo AI is that I don't know anything about AI coding and JK is bored by it (he made the AI so he should know). This doesn't mean that there will never be any diplomacy, but it means that if it will be made it will be so out of a sudden whim.
An outstanding AI might also see the day of light if one of you guys suddenly comes up with a simple yet brilliant system for a diplomatic AI that is unabusable.
Meanwhile you will have to wait and hope.