I hope no 4 strokes . 2008 was the last year my son raced mx competitively. I spent $6200.00 dollars on parts alone (except tires ) and most of that money was spent on engine parts . The 4 stroke mx bikes take WAY more maintenance than 2 strokes . But that new water cooled grossi engine looks interesting . May not make anymore power but i wonder if they could get more run time ? When bikes went from air to water cooling it was a big leap forward .