The four-stroke replacement for 250cc two-stroke racing will be unveiled at the Grand Prix de France this weekend. It's expected that the class will be replaced by 600cc four-stroke prototypes. The rules will be presented in proposal form, then considered by both the International Race Teams Association and Motorcycle Sport Manufacturers Association and should be finalized June 8 at the Catalunya GP. The new rules could be implemented as early as 2010.Despite heavy opposition from KTM and Aprilia, it's expected that the rules change will pass. To allow those companies time to adapt (companies who have significantly more experience racing two-strokes than four), it's expected that there will be a one-year moratorium on new teams entering the class, taking effect once the rules are implemented. Check back Saturday for full details.