Daniel Kaplan, Business Developer for Mojang, announced some pretty big news for Minecraft - Pocket Edition yesterday. The Pocket Edition team has begun to rework the game's code in order to allow for the generation of worlds that are much larger than those that are currently (and kind of disappointingly) available.
More stuff is planned to roll out along with it of course, including updated inventory and AI systems, and it looks like wolves maybe? There's no real indication of just how much bigger these new worlds will actually be, however it's definitely promising news. As of now there's no specific release date in sight, but it's definitely something to keep an eye out for.