This is interesting. the US does call for lettered cylinders only on EVO engines in micro and mini engines.
“5.5.1. EVO Engines
Evo engines must use a cylinder marked with lettered production code. Letters are different from one production batch to another.”
But you could read this as pure EVO, not upgraded PREVO. Not sure what the intention is but it was not spelled out. I could certainly see the desire to stop people from mixing the 2009 “super cylinders” with the new engines.
Also when reading the supplemental regs for Micro and Mini it is clear I was wrong on other details I have stated here. BAsed on conversations with Josh it sounded like there would be not changes to allowable micro jets witht he Evo engines (Rotax is still shipping with the 115-130 jet kit) Only regs in the supplementals on the XS carb refers you to section 6.8 in the full regulations (airbox regulations), actually should be 6.9. 6.9 does not specify any jet restrictions so micro should be totally open on jetting.