Technology inside, power, time in market, games on it will have much more in common with 8th gen than 9th.

Hmm, so if someone creates a Wikipedia page for the ninth generation consoles and just copy and pastes the Switch in the eighth generation page over, it would be a ninth generation console as far as the general consensus is concerned.
Great to know we are all on the same page. While we're at it, we should probably remove the DS from the 7th gen as it's not powerful enough and tell the Dream cast that it came out too early to count and the N64 that it was too late and that the Wii was too weak to be 7th gen and that 4 years to replace the Game boy advance was a mistake for our generation list.

Oh the tragedy that it doesn't make sense. Woe is me.
If only, if only, if only the Playstation 2 had come out later and more powerful it could have qualified to be amongst the Gamecube and Xbox.
The poor poor Wii U simply isn't good enough to be counted alone side the xbone or ps4. Oh if only the fools would have learned.

8th generation

Wii U: 2012

PS4: 2013 

Xbox One: 2013

Mid-gen upgrades of 8th generation:

Switch: 2017

PS4 Slim / PS4 Pro: 2016

Xbox One S / Xbox One X: 2016/2017

Btw Wikipedia lists Switch as 8th generation too. 

https://en.m.wikipedia.org/wiki/Eighth_generation_of_video_game_consoles

By the logic that PSP needed to use generic cables that weren't sold together (ignoring that the hw and fw itself supported it) then now that some smartphones are sold without charger then it must mean they have infinite battery right?

It can`t be any more obvious that Switch is a handheld first and with some tweaks to make it easier to play on the tv or share multiplayer.

Switch is not a mid gen upgrade, but an entirely new device with its own library.  Your logic is flawed.

Wikipedia can be edited by anyone, and therefore is open to people who mistakenly call it gen 8 to state as much.  That does not make it fact.  The bigger factor is how long it competes with the PS5 and XSX.  If it stays on the market beyond 2023, there is no denying it as a 9th gen console with hybrid functions.  And with the way Switch is selling, don't expect a successor anytime soon.

Couple that with the fact that it replaced the actual gen 8 console, and it becomes all that more clear that Switch is part of gen 9.

Personally I consider the Switch a mid-gen sort of thing, that would have been a 9th gen system, if Nintendo hadn't screwed up with their Wii U, which was unpopular and caused Nintendo to make a successor a little earlier than what was typical for them. The Switch 2 will also likely be a mid-gen sort of thing that releases in 3 or 4 years time, and a Switch 3 (or whatever it is that Nintendo decides to call their system) will probably release fairly close to the PS6/Xbox5 release, (maybe a year or 2 after depending on how popular the Switch 2 was) and they will all be 10th gen systems.

What I would find odd is the Switch, Xbox series X and PS5 all being 9th gen systems, the Switch 2 being classified as a 10th gen system when it gets released in 2023 or whenever, and the Switch 3, Xbox 5 and PS6 all being 11th gen systems when they get released between the years 2027 - 2029. That scenario would pretty much put the Switch 2 in a generation by itself, which as I said, I'd find that odd.

It is amazing how people can come with so many arbitrary and pointless arguments to defend the idea if a new system is replacing an old one, somehow it will belong in the same old gen. People just can't get a grip to look for the definition of generation.

The thing is, if Wii U wasn't such a huge economical failure, Nintendo could be able to launch the switch a bit later and all confusion regarding the time that it was released would be gone.

Now if Switch is a home console or a handheld... I won't bother with this pointless discussion any longer, a gaming console is a gaming console, a gaming system is a gaming system and a gaming hardware is a gaming hardware no matter if it's stationary or a portable one. Period. 

Switch play as both bc it's Wii U and 3DS successor's so it's obvious that you have every characteristics out of box. Switch is the living proof of how is so baffling that you are still trying to force this separation on Box A and Box B when technology and design have already evolved past this.

easier to study time line...

History have this all over their subject. For example instead of studying the whole hominin timeline... they divided it to miocene, pliocene, pleistocene.... gaming industry is being studied and will just keep on expanding. By having a defined timeline, it would be easier for people who read gaming history based on separate timeline.

in what sense can it be 9th gen? there is going to be a difference of almost 4 years with Ps5 release date

it can considered as last gen or mid-gen

don't care, the general consumer doesn't care, the sooner forum dwellers stop caring the better