*Update* MULTIPLE people from the FiM team have confirmed the title/description of the episode
*Update #2* Regardless of the actual title/description being confirmed, TV air dates are always subject to change.
Supposedly Season 2 will begin on September 17th 9AM eastern time. Someone from a TV listing company emailed me this information directly, and said he would get us some more proof on it tomorrow, though it has been floating around all morning on various forums/chans for pony.
Episode one is titled "The Return of Harmony" - Spoilered: Discord escapes from his stone prison and Twilight and her friends act quickly to find the Elements of Harmony to stop him. (Not sure why they are re-tracking them down if they already have them, but it's just a rumor right?)
Until it's all finalized, this is only a rumor though. The commercial a few days ago does sort of hint that the second season is very soon, so it's a very possible rumor.