Mojang has writter on its official site that there's no release date for the new features, but the developer wanted to give fans a status update.
"We’re working on restructuring a lot of code to allow significantly bigger worlds in future updates," the developer wrote. "We’re also updating the AI, inventory, and a bunch of other things. Unfortunately we don’t have a release date yet, but so far, everything is going to plan."
They also posted a screenshot from Minecraft: Pocket Edition teasing that a wolf, an animal that can be domesticated in other versions of Minecraft, will be added to the mobile version eventually as well.