I know for certain that I will have my Pinkie Pie-rate costume at DragonCon this year, and as long as there aren't any conflicts, will probably go to the "All the Pinkie Pies" photo shoot with it.
But, all told, I will have 2 MLP costumes: Previously mentioned Pinkie Pie-rate, and likely the Discordia (Grecian inspired genderbend of Discord). My husband will be bringing his Mage Twilight Sparkle genderbend costume, which matches in style to my Pinkie costume, and most likely the Roman inspired Celestia genderbend, which matches to my Discordia.
Still have no clue what days we are wearing what, since it is going to depend on photoshoots and panels for other costumes.
Party Pirate Pinkie Pie (MLP:FiM) 100%
Eris Discordia (MLP:FiM) 100%
Convention Line-Up: BronyCon 2013 - Dragon*Con 2013
Eris (Female Discord, MLP:FiM), Casual Gala Pinkie Pie (MLP:FiM)
The 10th Doctor, blue suit variation (DW), Queen Mab's Party Dress (Dresden Files: Cold Days), Party Pirate Pinke Pie