Wii was selling to a casual/non-traditional audience so once the novelty wore off sales plummeted. That doesnt apply to Switch since it is selling to a more hardcore/traditional gaming audience.

Next-gen is irrelevant, if PS4/XBO & NSW have had no notable affect on each others sales than there is no reason to believe PS5/XB4 & NSW will all of a sudden start harming each other.

Switch will likely start to decline around the time PS5/XB4 launch but that will be due to a natural sales curve rather than outside factors coming into play.

Mhm 3 years into the generation, PS4 sales were peaking, and they stayed really high the following year. By the time PS5 comes out it would be switch year 3. That's a pretty pre mature sales decline. 

Year 4, Switch released in March 2017, it's in year 3 now. A 3rd year peak followed by a small decline in year 4 is a pretty normal sales curve.

2013 2014 2015 2016 2017(peak year 5) 2018(sustained peak) year 6

ps4 peaked year 5/6 

so switch peaking in year 4 is pre mature. 

It released in mid-November so counting 2013 as year 1 makes literally no sense at all. Also 2018 had a 10% decline, that's not "sustaining its peak", thats a decline.

Besides, who cares when PS4 peaked? It had a later than normal peak, good for it but peaking in year 3 or 4 has been a very common thing for consoles.

What are you getting out of making nonsense arguments?

"PS4 was $399 it's first three years"

Yes and not up against considerable competition.

I'll give you there's less incentive to own multiple than, say, a 3DS. But like you said, there's still more incentive to own multiple than a PS4. Anecdotally, when I was doing Christmas shopping for my nephews the year we got them their Switches I initially insisted on one for them to share. When my mom found out what the Switch was, my explanations didn't matter. To her, it was a handheld that docked to a TV, and as such each of them needed one for themselves.

I agree with you. If a 3DS is a 1 in the "own more than one" factor, a Switch is a .5 and a PS4 is a 0... If we were to assign numbers to this.

So the XBOX ONE, PC, and 3DS/WIIU aren't competition. 

The point is why would anyone care about different models of the same console being lumped together.  I would like a breakdown, but that wouldn't change my perception that PS4 is still on par, so far, with NSW on weekly hardware sales.

Are you trying to say something about actual install base? Like 94m PS4s might be actually smaller cause some PS4 owners have both this or that SKU?  Id counter with how many NSW owners have multiple in the household because kids and portability.  When the Switch has new SKUs how many sales will go to households that already own one or more?  How can we possibly break this down into knowable double dippers?  Want an asterisk?  I guess won't change most peoples opinions.  

This is why we have hardware _and_ software.  The software is the real story in terms of money potential.  Of course software stats on this site are kinda neutered now.