Nintendo has officially revealed, indirectly, that the internet phenomenon known as Bowsette will not be appearing in New Super Mario Bros. U Deluxe for the Nintendo Switch and that she will not, at least for now, become canon.
Via ResetEra, this news was confirmed on the official New Super Mario Bros. U Deluxe website by the description for the new Super Crown item that can only be used by Toadette and will turn her into the “super-powered Peachette.”
Source: IGN.com Bowsette Won't Become Official, According to Nintendo