A bit of news straight from Jeb, who did a MC presentation at Dreamhack over in Sweden.
- No plans for dynamic lighting, due to performance and gameplay issues (Mobs spawning, mobs burning in light, etc.)
- Dragons aren't 100% out-of-the-question, but they most likely won't happen.
- Oceans (Basically just GIANT bodies of water) are probably not going to happen.
- There will be an item or something to make diamond tools more powerful.
- No plans for obsidian tools.
- Animals will be more persistent, only really spawning at the generation of a world.
- There's a possibility for infinite map height.
- Pistons will not push players/blocks far (This was seen in the pistons WIP video though, but he explained why)
- Adventure mode will be more rewarding to players who like to explore (Notch mentioned this a while back as well).
- NPCs are pretty much planned (Most likely for adventure mode, although he spoke like they weren't).
- There's a high possibility for "exclusive" items/blocks found in certain areas. Sort of like the jungles, corruption, etc. in Terraria.
Part 1: http://www.justin.tv/citricsquid/b/288355296
Part 2: http://www.justin.tv/citricsquid/b/288361863