Call to Arms is meant to lower wait times by offering additional rewards for queuing as the currently least represented role. To be eligible for the additional rewards you must solo queue for a random level-85 Heroic in the role that is currently being Called to Arms, and complete the dungeon by killing the final boss. Every time you hit these requirements (there is no daily limit) you'll receive a goodie bag that will contain some gold, a chance at a rare gem, a chance at a flask/elixir (determined by spec), a good chance of receiving a non-combat pet (including cross faction pets), and a very rare chance at receiving a mount . . . (Source)
So, this is interesting. I for one am fuming. Yes, I benefit largely from this, but at what cost? My boyfriend can't benefit from this at all on his hunter and my guildies are going to be shafted since it comes down to helping guildies or farming these mounts? So I'll be single queuing until I get them. Not to mention I feel that it is overcompensating players who play hybrid classes while completely shafting pure DPS specs when, personally, I found that "faster queue times" was usually incentive enough. I don't know, I feel like it's just going to bring about a lot of sour grapes.
But what is of interest for us gold-makers out of this?
". . . a goodie bag that will contain some gold, a chance at a rare gem, a chance at a flask/elixir (determined by spec) . . ."
Gold, meh. Flasks were already in the unprofittable range for most. But what interests me is the chance at a rare gem. You see, if this is meant to be an incentive to queue for randoms they'll need to keep the rewards on par with what people need. Therefor, it stands to reason that when epic gems are introduced they will replace rare gems in these bags.
Certainly this will not be the only source for epic gems, but I believe this will put them into the economy at a faster rate than may have previously been expected. I know that, if I don't already have all the mounts I need, I may find myself chain running in hopes of mounts and epic gems myself!