This past Saturday, we saw the CMC's get called for the first time by the map. Last year we saw Starlight and then Spike get called. And thanks to DF's Preview, we know Sunbust and Starlight will get called, maybe even Zecora later on as well.
But who else should get the call?
Well, I feel that the 200th episode should have the map call this ponies : Lyra, Bon-Bon, Octavia, Vinyl, Derpy, and Sunset Shimmer. And have this occur while the Mane 6/7 are on current Friendship Mission. And have Sunset get call by the emblem on the Journal start to glow rapidly.
Others it should/could call are : Luna and Celestia, Cadance and Shining Armor. It could also call the Student Six, It could Thorax, it called Ember (just the look on Ember's face when she finds she's been called to solve a Friendship Problem would be priceless to see), it could call Trixie, It could call Moondancer and Minuette, it could call Big Mac. Soarin, Spitfire, Tempest, Skystar, the possibilities are endles