With the introduction of Scenario's you could say that the first step to PvE content that can be run without tanks has been made already.
Then there is the age old "complaint" that people have to wait for Tanks to join before they can run content and the fact that some other games out there also have pve content without the classic tank.healer/dps triangle.
Could the good ol' "sword and board" be purely cosmetical in the future?
And if so, would you like that, or not?