Alternatively they could make "New Super Mario Bros. Switch" instead. That would be the preferable option.
Why on Earth is everyone so obsessed with ports all of a sudden? I remember years back Nintendo was (unfairly) criticized for re-releasing and remaking everything and now people are practically asking for it. So weird.
Like you I would be most interested in a new Mario game compared to a port, but I think a lot of Switch owners skipped Wii U so some of the port excitement comes from there. On a separate note, I believe around the time Mario Maker released for Wii U, Tanaka mentioned that they were planning to challenge themselves in a new direction for the next 2D Mario game. As a result, I expect the New series has been completed for now and we will see something entirely different for the next game. I love the New series but I'll be glad to see something different.