There is speculation that the -10MAX does not have the MCAS system, as the additional length moves the CoG backwards, so it flies like the NG's. If the -10MAX is certified as an NG variant then it could fly while the -8 and -9 are grounded. There are a lot of if's and buts there - if Ryanair do order, my guess is it would be the 737-10 variant and the MAX branding would be dropped, as Mr. Trump suggested.