I guess it depends how strong the first half of 2019 will be for the Switch and how weak will be the first half for XOne.
But Im imagining that the Switch will be able to reach their 20 million sales projection for this fiscal year.Hell I even expect it to sell one extra million or two more than Nintendo expects(simply because it seems that it did better than anyone think this december).So that would put the Switch betwenn 38 to 40 million.
Then Nintendo would have to sell an extra 5 or 6 million, give or take, betwenn April and June.If Animal Crossing launches by the end of June, coupled with Fire Emblem, god knows what else, and the increased Switch momentum(I dont expect the Switch to sell less, in 2019, than it did this year) they may be able to pull that number.
And yeah, with gen 8 dwindling down, I dont expect XOne to pull big numbers betwenn January and June.So with 45 to 46 million units sold, Switch should at least match and most likely pass the XOne.
Oh, and those are shipped numbers of course, since we would be using Nintendo numbers.I know this is bold and not so easy to accomplish, but I feel that this might just happen.
My (locked) thread about how difficulty should be a decision for the developers, not the gamers.