They're decent numbers. Not as great as the 360's were when its own slimline model came out, but still good. The real test will be the coming months. The 360's best sales period was the 22 months from June 2010 to March 2012. If the XBO cannot sustain a baseline in 2017 stronger than its previous baseline, then there's a reason to worry. At minimum, I think the XBO needs to consistently sell at least 25% more units throughout the Jan.-Aug. period for the XBO S to have been considered a success. If YoY growth is modest, and especially if it starts to taper off by mid-year to where sales are flat YoY, the the XBO S can probably be said to have only kept sales stable, and that's not what I'd call "successful" for a slimline model.
I Wonder if Microsoft will release some Xbox One numbers after the release of Scorpio.