Seems that Mojang, the company behind the wildly popular Minecraft, does not make many changes to the world generator very often as it causes issues in the game that are noticeable to players. They decided it's time and are making some large changes to it.
The last changes made to the world generator were back in March of 2012 when they added the jungle biome. They have decided they are going to address several problems in the way the worlds are created.
- Too large oceans
- Too uneven/random biome placement
- Not enough variation
The solution to these problems have been,
- Tweaks to add more islands and checks to avoid huge oceans
- Biomes have been put into four main categories: snow-covered, cold, medium, and dry/warm. Biomes will avoid getting placed next to a biome that is too different to itself (sometimes this still happens, but it's very rare now and not all over the place)
- We've added a whole bunch of new biomes…
- … and most biomes have uncommon/rare variations that you may run into
- We've also added a bunch of new terrain features, such as new flowers and trees
The new world generator should see the light of day in the Minecraft 1.7 update.