According to a report from Nintendo Soup, Eiji Aonuma who is the series producer on The Legend of Zelda said that there is a possibility that the next Zelda title could still be released on the Switch. Exactly when that will happen remains to be seen, but Aonuma suggested that it was a possibility.
He also went on to state that Breath of the Wild had yet to fully use every feature of the Switch’s console, indicating that the next title could incorporate more features that would take advantage of some of the Switch’s features. Nintendo had previously stated that they plan to support the Switch for longer than a console’s traditional life cycle, which is around 5-6 years.
This means that even at the minimum, it still gives Nintendo plenty of time to create a new Zelda title for the console. As to whether or not we will see a Zelda title for the DS handhelds remains to be seen, but given that the Switch is just as portable, it seems unlikely, but we could be wrong.