Minecraft Forums

If you load the world normally with the new update, you shouldn't loose your stuff, but if you're really worried or want to generate a new world but keep your structures, try mcedit. You can copy a selection of land that you've changed and import it into another world, It'll even keep all the items you've put in your chests.http://www.mcedit.net/

Quote from Eliminator

Yah, I know about that, but is there any way that I can merge 2 worlds where all the blocks that are the same get removed?

Can you explain that a little more?

When minecraft generates a new seed, the world could look completely different, and as a result your house could end up buried underground, halfway in a mountain, or floating in mid air. I would just use mcedit, or put your world into the newest version, and explore out until new chunks generate. When the new chunks start generating, it will from there on generate all the biomes in the new update.