Johan uses Reddit to give out information regarding MCPE. And here's what i've found

~For 0.7.4:

1. On August 17 Johan Said : We will see how quickly we want 0.7.4 to get out to fix a few bugs, we might submit on Friday and then it's a bit tricky. But new cool stuff is in the works.

2. On August 18 Johan Said : we are considering to add flint and steel in creative to 0.7.4

~Other updates (0.8.0 - 0.9.0)

1. On August 17 Johan Said : New biomes and stuff is planned for the 0.9.0 version

2. On August 17 Johan Said : Infinite worlds are currently planned for 0.9.0. We wont simply make worlds infinite, we will also add some stuff but thats in the works.

3. On August 17 Johan Said : We will probably add more difficulty modes.

4. On August 17 Johan Said : Rails in 0.8.0, redstone after 0.9.0, the powered rails will always be powered. You will be able to mine redstone and use it for making powered rails, but it will only be used for making items, you wont be able to place it.

5. On August 17 Johan Said : We hope to add caves in 0.9.0, we will see about dungeons, mine shafts, and villages