It looks like they actually mention a season three of FiM if you dig a bit. I'm pretty sure all the music for Season two is complete at this point (Don't quote me on that), so I supposed it would be inevitable that they would be looking toward the tracks for the third.
You can find the article here.
And the quote from it:
And if you’ve ever wondered what an opera singer might do in her time off stage, Chan-Kent has an interesting sideline; she’s an voice-over actress, going into her third season with the animated My Little Pony television series. “I do Silverspoon, the little sister pony, and I do all of the singing for Pinky Pie...”Thanks to everyone that pointed it out! I tend to miss things when I'm in email grind mode.
There's a nice little ponychan thread about it going on at