I'm pretty sure it's no secret or even a slight mystery that there will be way more pony after season three. Friendship is Magic is one of the most popular shows on The Hub, and My Little Pony is an icon at Hasbro. With the incredible success of the current Generation 4, we probably won't see an end anytime soon.
Enigma Sage dug through some of the DHX investor relations documents to see if anything pony related was mentioned, and it looks like we have a bit of season 4 buried in the fine print. More specifically the line found below:
For Q4 2012, the Company earned $6.71 million for producer and service fee revenues,
an increase of 67% versus the $4.02 million for Q4 2011, which marks the 4th consecutive quarter of growth in this category when
compared to the same quarter for Fiscal 2011. DHX Vancouver earned $3.19 million, an increase of 61% (Q4 2011-$1.98million), and DHX Wildbrain earned $3.52 million, an increase of 73%, for Q4 2012 (Q4 2011-$2.04 million). For Q4 2012, thebreakdown for major projects over $0.10 million for DHX Vancouver was $1.63 million for My Little Pony Seasons 2-4, $0.91million for Little Pet Shop Season I, and $0.65 million for Pound Puppies Seasons 1-3. For Q4 2012, the breakdown for majorprojects over $0.10 million for DHX Wildbrain was $0.60 million for Monster High Season 13, $1.45 million for Oki’s OasisSeason 1, and $1.39 million for How to Train Your Dragon Season 1 which, as previously disclosed, wraps up the Company’sinvolvement in this series.
While its not a complete 100% confirmation, I can't imagine what else DHX would be signed for that includes "My Little Pony" and "Season 2-4" in the mix. So unless FiM combines with another show, converts into a new generation altogether, or Hasbro is hit with a meteor from space, we will probably see a season 4 eventually.