The FIM has announced that there will just be a single class in the FIM World Supermoto Championship in 2010 - S1, the 450cc class.

The following is from the FIM...

During a meeting at the FIM Motocross Grand Prix of Portugal in Agueda, on May 10, the Motocross/SuperMoto Grand Prix Commission, composed of Mr. Giuseppe Luongo, President of Youthstream, Dr. Wolfgang Srb, President of the CMS/FIM, and Mr. Takanao Tsubouchi, MSMA Secretary General, unanimously decided to run one class only in the 2010 FIM SuperMoto World Championship.

Changes to the FIM Regulations are in bold characters.

For application as of 2010:
042.4.2 Classes
The recognized class for the FIM World Championship is the following:
S1:
Championship for motorcycles of Cat. I, Group A1.