Pachter is on the right track about the predictions being too high, however, it's highly plausible that a price drop will recompense for the over anticipation of holiday titles to push hardware alone. Especially with that leak (not saying I believe it) of a Switch Pro happening next year which stated that the current Switch will receive a price drop. But even leak aside - I'm pretty sure a price drop is the only way to sell 15m+ this fiscal.
I think 15 million is more likely unless they have a publicly impactful fall direct or something that produces unprecedented sales for a Q4 and Q1. Because so far Q2 and Q3 ending have only done slightly better than last year's numbers. And this doesn't include the explosive launch month of 2.7m+ sold (?) don't remember the figure exactly.