Even with out fire sales, and a new console, if we look at previous years, xbox has been selling 2-2.5 million during the holidays. yea box lost momentum last year, but switch might do the same in the future.
Switch will not slow down any time soon. The sheer amount of system selling games being released will see to that. That's before you consider price drops to keep up good momentum and Nintendo's ability to appeal to a broad market.