A Create a World page was added to TS3.com It has the info about it but no download link….yet

The Sims™ 3 Create a World Tool – BETA*
Create your own worlds for The Sims 3

Put the power of world creation into your hands!  Create and share unique new worlds that you design with The Sims™ 3 Create a World Tool – BETA.  Download for free and step into the shoes of The Sims 3 development team by using the same tools the team uses to create worlds and towns for The Sims 3.  Design and build entire worlds for your Sims, or begin your creations with pre-made Sunset Valley or Riverview terrains. Expand your creativity, and share your creations online through The Sims 3 Exchange.

FEATURES

• Design entire worlds for your Sims, from choosing terrain patterns and roads to placing lots, vegetation and neighbourhood accents like water towers and lighthouses.
• Start with a blank canvas, or modify the terrains that formed the basis of Sunset Valley or Riverview.
• For advanced designers, bring your creativity to life by creating and importing designs from Photoshop and other graphics programs.
• Expand your landscape features and building options with The Sims 3 Create a World Tool – BETA with The Sims 3 World Adventures expansion pack, or items from The Sims 3 Store.
• Share your worlds through The Sims 3 Exchange.

* PC Only

[Thanks go to SimPrograms for that! ]