Ducati's rear wheel spoiler/tire cooler declared legal and within the rules and Ducati and Doviioso's win at Qatar will not be taken away. The MotoGP Court of Appeals denied Honda's, Aprilia's, Suzuki's and KTM's appeal to make Ducati's rear wheel spoiler/tire cooler illegal. That was denied by the court. This weekend they will be racing in Argentina. How many will line up with similar setups? I am willing to bet by the time they race at Austin in several week's time almost everyone will have one.
http://www.motogp.com/en/news/2019/03/26/motogp-court-of-appeal-issues-ruling-on-ducati-aero-case/287196