When New Super Mario Bros. launched for the DS in 2006, it brought back the classic side-scrolling the franchise was known for. Then came New Super Mario Bros. Wii, New Super Mario Bros. 2, and New Super Mario Bros. U. The series has been positively received, though interestingly none of the titles have reached a 90 on Metacritic. New Super Mario Bros. U released in 2012, and was revisited as a theme in Super Mario Maker in 2015. Since then, the New Super Mario Bros. series has remained quiet (though, Super Mario Run uses the NSMB U graphical style), but that could be about to change, if rumors are to be believed. New Super Mario Bros. U may be getting a Switch port.
The site ComicBook states that it has been "following up on these rumours (the article refers to "sources connected with Nintendo of Europe" that apparently have provided accurate information before) with other tipsters linked with Nintendo who have corroborated these suggestions." According to the site, "multiple tips" state the port will include New Super Luigi U. (This was an expansion where players controlled Luigi, and included new courses.) ComicBook also states that "some sources" indicate that the port will feature "new content of some description," though specifics weren't given. Finally, the site has a potential title for the port: New Super Mario Bros. U Deluxe.
There are a few things to consider here. Nintendo has ported games from the Wii U under the "Deluxe" title. The most popular may be Mario Kart 8 Deluxe, with a score of 92 on Metacritic, putting it in the top five highest-rated Switch titles on the aggregator site. (It even surpassed the original Mario Kart 8 for Wii U, which has an 88 on Metacritic.) Nintendo also released Pokken Tournament DX. There are also ports under a different title, such as 'Definitive Edition.' Hyrule Warriors and Rayman Legends were ported to Switch under 'Definitive Edition.' Of course, Nintendo has ported games from Wii U with no added subtitle, such as Bayonetta 2 and Donkey Kong: Tropical Freeze.
Thus, a port of New Super Mario Bros. U wouldn't be totally out of left field. At the same time, it's doubtful that many have actually requested a port of the game. Re-releasing it would make it seem like Nintendo is buying time until the next big game. It would also be shocking if Nintendo ported this ahead of Super Mario Maker. Mario Maker for Wii U has received no support from Nintendo in a long time, and yet new levels are still being uploaded from players. A Nintendo Switch port of that game would make more sense than New Super Mario Bros. U.
Nothing is confirmed of course. At the very least, those whose first Nintendo console is the Switch will be able to play New Super Mario Bros. U for the first time if the rumors turn out to be accurate.