Xbox has too far of a lead. According to top industry analysts, Switch is only on track to sell 8 million this year. If Nintendo only does this for 2.5 years, by my calcoolations, that's only 32 million Switch units sold against Xbox One's... I dunno... 50-55 million units? To be conservative!
It's on track but the Switch could break the 300k per week threshold when Smash and Pokemon arrive thus considerably upping that 8 million forecast to maybe 15 mill. If Mario Tennis was enough for the Switch to hover around 200k units I would think Smash Bros will sell more units.