You're not really giving any concrete reasons why you believe that though and I've explained in multiple ways why it's unlikely to happen.

PS1/PS2 had such great legs thanks to emerging markets, those markets have grown significantly since then and PS4 got off to a much stronger start.

PS4 has been dropping at a faster rate than PS3 for the last 3 years.

PS3+360 were not popular entry-level alternatives after PS4/XBO released at $400-500 despite being sub-$200 with discounts to $100-150.

There is no if about Sony being stubborn with price reductions, the Slim & Pro models released over 3 years ago and have never gotten a permanent price cut and they have gone with the same price for 3 BF in a row.

The combination of all these things means that PS4 is unlikely to have extraordinary legs after PS5 releases, it will be just like PS3/360 and be an afterthought once the successors releases.

I just find it hard to imagine PS4 not selling another 26 million from now until its discontinuation given how quickly it's reached 100 million and how strong its sales still are. PS5 is looking likely to be more expensive than PS4 at launch so I don't think it will kill off its predecessor as quickly.

I got Switch coming through in the end, but just barely. Around 120 million for both

Stockholders don't give a shit about console lifespan. They don't get a bonus if hardware hits any paritcular target like in year 6. They don't give a crap about that and they shouldn't really. It doesn't boost stock price, stock price is based on the current fiscal status of the company (that fiscal year namely). They want to see strong sales every fiscal year, not "well we shipped 20 million ... two fiscal years ago", the problem for Nintendo is by 2021/2022 they're going to have exhausted most of their franchise catalog, there will be likely by then at least 2 3D Marios, 2 3D Zeldas, 2 full blown Pokemon games + Pokemon Lets Go, etc.

Nintendo's business for many years has always gotten new hardware every 4-4 1/2 years, so any time a console or handheld was in the back half of its product cycle they always had a new console or handheld coming to refreshen the business cycle. So like for example when the GameCube was dying they had the Nintendo DS coming out while the GameCube was still relatively young (only 3 years old in Nov 2004), but that created a boost in yearly hardware shipments all the same. And when Wii was fizzling out, they had the 3DS come out when the Wii was only about 4 1/2 years old.

The staggered nature of the handheld and console hardware lines meant Nintendo enjoy a nice business shot in the arm quite regularly. 

Stockholders don't care about handheld/console delineation, hardware shipments are hardware shipments and Nintendo gets their profit margin on any unit of hardware.

So I think that will be a challenge for them now that they only have one system, will stockholders and Nintendo's own business suits which have gotten used to the old model be "OK" with 2-3 years of shipments in the 8-12 million total hardware unit range. I'm not so sure they want to do that willingly (they were kinda forced to sustain themselves for a couple of years in that range because the Wii U flopped and 3DS was cratering in its back half, they had no choice because a new system wasn't ready ... but I doubt Nintendo willingly wants to ever go back to that level of hardware shipment again). That's one of the downsides of only having one hardware line.

When you will come back to Earth read that : http://gamrconnect.vgchartz.com/thread.php?id=241496&page=1

So much for monstrous numbers in China.

I expect the Switch to win in the end, with Switch winning in the US and Japan more than making up for Playstation's lead in Europe. And then there's China...

I really wouldn't put any stock in China making a difference. Chinese Media reported the XBO sold 100k in it's launch week, while Niko Partners is reporting 50k Switch's sold day one, with 100k sales estimated by the end of 2019. China just isn't a big market for consoles and won't be any time soon, and the terrible Switch they just launched that's region locked and only has a single game... yeah...

Switch isn't the console that's going to tame the Chinese Market, and I don't expect any console will for the foreseeable future.

I dont think its region locked, just the online is.

I saw someone mention it being locked while PS4 wasn't. I guess online/eshop is what they were talking about then.

When the dust settles, PS4 will be the #3 best selling video game system of all time, and Switch #5.

Not bad considering both came after their respective companies worst selling consoles to date.