I'm trying to work out if you're asking if it will outsell it before the next Xbox comes out, or if you're asking if it will outsell the Xbox lifetime.
Because lifetime is an obvious win for the Switch. Xbo will sell under 60m lifetime. Switch will do more then that.
Will have outsold xbo before the end of 2020.
Predictions (Made July 2019)
LTD: PS4 - 130m, Switch - 110m, XBO - 52m 2019 : PS4 - 15m, Switch - 18.8m, XBO - 4.8m 2020: Switch - 22m (Peak Year)