Even though the PS4's the clear market leader at the moment, I'd say the Xbox One's numbers are still respectable. Microsoft had a lot of damage controlling to do this generation, and to close in on 20 million is an impressive feat.
Now, how much is sells in comparison to the 360 is another thing. And we should also consider the rumored upgrades as well and how they will count in terms of the sales for the generation.
Chip manufacturers might know. I saw IBM's numbers for last gen consoles during a visit to IBM several years ago alongside a popped open 360 and PS3. I don't know what their source was, I just remember that the 360 was ahead by like 10-15m units at that time.
No idea. Not in that chart, at least. Whenever a Sony product fails, they go to great lengths to obscure any unflattering numbers from the public. If you google "Nintendo hardware sales", you'll find a page on Nintendo's website with LTD HW/SW sales for Wii U as of Dec 2015. I very much appreciate that kind of transparency.