Warning: All of the following information is complete rumor, speculation, and possibly spoilery. It has merely been posted for the sake of discussion, not confirmation. Please proceed at your own risk.
EDIT: The tumblr post provided as source had to be removed by its author and does no longer exist.
DerpySquad, a member of the illustrious Derpyhooves News,
So, humans. Mind you, this isn't definite yet, but there's certainly a lot of evidence in its favor. To summarize:
- Hasbro has recently announce a new IP based around MLP that's aimed at teenage girls, filed under the trademark "Equestrian Girls", which is for clothing, dolls, and doll accessories. Also, perhaps to defend the trademark, the website equestriagirls.com was recently taken down.
- The tumblr post states the new movie that Hasbro has been producing may have a plot involving the ponies falling into a portal and ending up as humans in an alt universe.
- The lessened length of season 3 may have been to redirect more resources towards developing their new IP. The new direction would at least make business sense, as a new IP designed to compete with other tween doll lines. Tying their new dolls to an already massively popular franchise would all but guarantee sales. Also, Hasbro themselves prefer to make tie-in shows with their merch to boost sales.
[update here] This all turned out to be true :(