Not true. Xbox sales were good for the last part of 2016. And based on this info we have from the insider the XBO has an install base of above 28 million by the end of 2016. First few months of 2017 sales of the XBO weren't that bad compared to previous years but the sales did take a drop but went back up in November and December. US sales make up 55%-60% of XBO WW sales and it sold just under 4.3m this year in the US so WW sales for 2017 are probably 7.1m-7.8m which puts the XBO above 35m.
Only if you assume that it’s still 55-60% and not quite a bit more. Even the UK have been strongly favouring PS4 lately. X1S dropped heavily in sales this whole year WW, I remember Shuhei Yoshida even stating that they had sold 3 times the amount since the beginning of the year at last year’s E3.