It seems switch is eating Xbox volumes mainly, ps volumes remain the same as pre-switch launch. Anyone else?

Too little info to make that conclusion.  Consider game releases.  I'm sure there are other possible reasons too.  

I think a lot of the time people think one console eats into the sales of another. While this can be true to an extent, I think consoles more or less just co-exist and coincide with each other. Xbox One is outselling Xbox 360 at sales rate(iirc), Playstation 4 is outselling PS3 at sales rate, and Switch is outselling Wii U. All will be successful, and while Switch might eat into sales of Xbox or Playstation a little, it's more likely that all demographics will keep expanding more and more.

Xbox sales are already low since the beginning. They don't need Switch to accomplish that.

I don't think the difference between volume matters since they all use the same TV. Unless you have them hooked up to a different TV.

Oh you're talking about sales. I mean Xbox one is probably going down not because of the Switch but because of the PS4. When one goes up the other goes down. Think of it as a see-saw. The Switch won't effect any sales for awhile.

So it's not possible that people just buy the Switch and X1 sales tank as usual?

i love the switch because of how accessible it is. it's fun to play on an hdtv, but if you're too busy to lounge at home then you can play it portably.

the switch reaches a market that both xbone and ps4 don't. if anything, i can imagine switch probably eats into 3ds sales more than those two.

my observation was rather on the platform market share dynamics. Without pure mobile devices, and making an abstraction of wiiu, Ps holds 2/3, Xbox is now sharing that 1/3 with switch. With switch eating up Xbox share.

That thread about which two devices to own.... pretty sure PS4+Switch won out by a rather large amount.
Also very few picked Xbox + Switch.