We used to have Call of the Mists and Greater Call of the Mists buff while we still had esports events. We don't really have any kind of boost in PvP, like ever. My suggestion is that we should get these buffs back, for example, as a bi-weekly event (excluding custom arenas).
For those who are not sure what it is (this is the greater buff):
+15% PvP Rank Points
+25% Reward Track Progress
+200% Magic Find (PvP Only)
This would be a very low investment from Anet's side, and basically without any risk for the players. Some healthy promotion for PvP is always good, bring some fresh people in, and the game quality won't change for most people. Good thing about this buff that it applies in unranked too, so it's not forcing people to queue for ranked, ergo complaints about 'new players ruining ranked' wouldn't really stand. Small amounts of reward track gain boost is not going to have any effect on the economy. PvP rank is farmed in custom arenas anyway, but this would at least some kind of incentive to run unranked. Also, there are people who like to get their rank using the old fashioned way (playing the game).
I was also thinking about linking them to AT-s (do we have it? I don't think so) but I firmly believe a less stricly time based Mists event would be better.