Well, so far over 40% of voters would answer that with "never".

The PSOne (small redesign) launched in July (Japan) & Sept (US/EU) of 2000 at $99.99 and got a price cut to $49.99 in May 2002. It shipped 28.15 million by the time it was discontinued in March 2006.

What the OP raises might be a possibility but I'd say it's totally contingent on these two key crucial aspects as to how it'll play out in the future ...

1) Timing

With the above it'll rest on how far protracted Sony wants this current generation to last and how short Nintendo wants their current system to last before the release of a new one. If Sony can afford to push the release of their new system by late 2021 then it raises the chances of PS4 reaching above 150M units. On the other hand, if Nintendo decides to cut it at late 2022 which may not be all that unreasonable of date to launch a new system so there is potential in that case the Switch could have it's legs cut somewhat short by it's successor ...

2) Pricing Strategy

The plans regarding this will rest on how aggressive Sony will be in the coming years including maybe leading into the next generation or what Nintendo might possibly do as well with the Switch. If Sony starts creating a free fall of the price of PS4 such that they'll cut the system by $50 every year starting next year up until it reaches $150, there's a real possibility in that instance where Sony could really ramp up some more growth in developing markets like Latin America, Eastern Europe, Middle East, South East Asia, some parts of Africa along with mainland China as well since they perform very well outside of traditional western/japanese markets. As for Nintendo with the Switch, they might not decide to have a price cut at all next year and hold off their first official price cut or put out a lower price SKU until 2020 and we might not ever see more than two prices cuts either which could total out to the system never costing less than a $200 price point. More specifically if Nintendo decides to hold out the Switch's price at $250 and above for the majority of it's life it could raise the possibility of stunting the systems sales in it's later years since by the end of 2019 all of their staple franchises will have released which makes it far harder at that point to grow the systems userbase without price cuts or serious holiday deals ...

Then we have the Xbox One could probably sell to as much as 60M units ...

Basically Sony would have to try to maximize PS4's hardware sales as much as possible once next generation takes root and Nintendo would have to hold off and minimize the Switch ...

a

Those generation numbers are arbitrary.

If Xbox One can do close or over 60mil, while Switch does beat the 3DS and PS4 is below PS2. Then It should drop below 50%

If you mean against X1 and Switch, it will be very very hard to achieve 50% market share.
But Nintendo fans need to have a consensus if Switch is same gen as PS4 and X1 or not, because several like to put it as gen 9 even if weaker than gen 8.

Gaming media sites does put Switch in the same gen as PS4 and Xbox One. Especially how much we compare the Switch to those 2. 

Switch is not the same gen as PS4. PS4 already won this gen against X1 and Wii U. Regardless if people want to forget about the Wii U just because the Switch is selling well, the Wii U happened. Get over it.

Lame excuse.

So WiiU is last gen and should be Wii+WiiU winning against PS3 and X360 or was WiiU this gen and will be WiiU+Switch against PS4 and X1 with next gen PS5 and X2 having no competition for a long time?