But before that ever happens I feel like we might get cross-server market board, free companies and cross-world linkshells become the new default. I remember Guild Wars started with the whole servers being separated yet you could guest visit other ones. Then eventually the server data got merged and the only true separation is regional. I don't recall if it was the same with WoW though.
I have a feeling we see, in rough order:


Cross-Datacenter Marketboards

Regional Party/Duty finder

Regional Marketboards

Cross-Datacenter FC's

Global Marketboards (ala GW2 / CoX / ect)

Regional World visit