Well, as of the end of 2017, the XBO is still running a surplus of a bit under 1.5 million units in the U.S.
However, after 177 weeks on the market, the XBO is only at 90k LTD in Japan, whereas the 360 was already over a million, with the XBO having a net deficit of 917,446 units according to Media Create data, so that alone erases nearly two-thirds of the surplus from the U.S.
According to VGC, the XBO has been continually trailing the 360 for most of its life, and is currently running a deficit of over 2 million units in the region. That erases the remaining surplus from the U.S. and then some, netting a total deficit across of the main three regions of about 1.59 million. Not quite as bad as the 2.3 million deficit being reported by VGC, but VGC is currently undertracking the XBO in the U.S. by something like 800k units, so they may be off for Europe as well. Still, it's clear that the U.S. alone is insufficient to yield a net surplus over the 360 for the XBO.
And Zhuge is right that the XBO's surplus in the U.S. will vanish as well. The 360's fifth full year was 2010, the year the 360 S was released, and that caused 360 sales to skyrocket. Just to keep from being down LTD vs. the 360 by the end of this year, the XBO will have to sell at least 5.27M for the whole year. That's a YoY increase of 23.3%. That's simply not going to happen.