Ps4 is on the 70 millon now. I guess we can expect 90 at least for next year and more than 108 by end 2019. That tops PS1 at less than 105 millon and Wii at arround 102. 

Reasons: XBox one X is faster, but too expensive and this holiday ps4 is still doubling xbox in numbers. Xbox doesn't have great exclusives in the near future.

Switch launched Zelda, Mario and Karts. Besides that Ps4 managed to pass 20 millon this year. I don't see Switch taking many customers from PS4. The way I see it Switch is not a home console that can be portable, Its a portable that can be conected to a TV. So my point is that switch has the people from the wii u + some casuals + all the nintendo 3DS mobile gamers that are upgrading to the best mobile console ever with great games. Customers are mobile gamers and thats why its exploding in japan.

The ps4 has the pro, it doesn't add much on sales, but one customer can buy it and it will be counted as 2 PS4 sold. (I have 2 ps4 pro and sold 1 standar, so i bought 3 through time). That did not happen with other consoles before.

Comparing to PS2, PS2 sold close to 160 millon consoles, and it will be difficult to reach that amount.

But PS2 had an advantage. When PS3 launched it was really expensive at 600 USS. If PS5 goes out on 2020 or better 2021 and at 600, then I can see the PS4 going for the 1st place in history.

Also PS4 can lower its price. At 150 US could sell very well in developing countries and as a casual console too. 

There is a posibility that also PS4 pro will run PS5 games at lower resolutions becoming a cheaper option for many.

Also 4k TVs will reach more market in 2020 and a cheap pro will be a nice cheap upgrade for people selling the old ps4. This also is the 1st time that happens. Imagine you can sell your ps4 at 125 - 150 uss and buy a pro at 250 if you care about visuals and will count as another PS4.

Game wise, 2018 will be big. I can see Dead Stranding and Last of Us 2 as 2019 big sellers. I can expect another From Software game, another GTA and another battlefield placed on WW2 or modern days after COD WW2 hit. 

Another little boosters will be cheap PSVR and the fact that the network of friends and where they play is more important than ever on the decision of buying a console.

Coming back to the post I can easily think that PS4 will become 2nd best selling home console in history by  xmas 2019. 

Ps1- 105m

It'll be close. I don't see it doing a 20M and 18M for the next 2 years though.

Easily imho. This year will probably be its peak year easily topping 20m and if it will get a permanent price drop to 199,-, which it will, I can see it hit the 20m in 2019 as well, as long as TLOUp2 releases that year.

104.25 millions is the set bar, but who knows.

The price range of the Ps4 is seems to be something near of what the Ps2 had, they easily could put a permanent price of $199 this year and $149 for holidays 2018 and $149 for the entire 2019.

At some point the Ps4 will reach the sweet price of $99.

Too safe of a prediction, I would say.
Step your game up, pal
:P

Probably, let me think. Let say we have 72 millon PS4 sold, with 20 more 2018 it will get to 92. With 10 more before Black friday 2019 can be at 102... So I think it will be between BF and Xmas 2019, very risky to say for sure it will get to 105 before BF 2019. 

But. If this year finishes with 75 millon  consoles sold, then yes. It can be done before BF 2019.

oh wait.....I was under the notion that playstation 1 sold 102M units.....my mistake..

yeah, its it bit more risky with 105M...

PS4 is definitly on track to see $149.99 and $99.99 in the future. I can see a digital only Super Slim with 500GB of Flash hitting the market to address the super casual.

At O.P., I think PS4 will outship PS1 by Q1 or Q2 2019. Shipments should be at 78 - 80 Million as of Dec. 31, 2017. Another 25 million units in the next 15 - 18 months looks very likely.

That is a bold yet possible prediction. I haven't realized how well the PS4 has sold.