Considering how you predict 110M for PS4, not really.

You think the lifetime gap between PS4 and Xbox One is going to be 37M.

PS4 is currently at 62M, while Xbox One is currently at 30.5M, a gap of 31.5M

So you think that PS4 is going to sell 48M for the rest of its life, while Xbox One is going to sell 42.5M for the rest of its life, even though Xbox One has consistently been outsold by PS4 by a factor of over 2 to 1 for its entire life and is now being regularly outsold 3 to 1.

After a while, every console hits a plateau in sales. I do think the PS4 will be over 100M, seeing as it's tracking with the PS2. I think the Xbox One is still selling well. Just not as well as the PS4. So that 73M is still realistic to me. Nothing more than 75M. I don't think it's a stretch. My optimistic comment was really toward those that think the Switch will beat out the PS4 in LT sales. While the Switch is selling quite well. It's still too early to say that it will beat out the monster that is the PS4 (saleswise). Sony pretty much has the rest of the planet in it's hands. The fight is closer in the US and I believe the Switch will overtake the PS4 in Japan. That's about it though.

So you do expect Xbox One to start selling as well as PS4? At the end of this year, the gap between the two consoles is likely to already be 37M. Xbox One: 36M, PS4: 73M. Mathematically, the only way for Xbox One to sell as well as you expect it to sell compared to PS4 is for Xbox One to start selling as well as or better than PS4 after this year.

Anything is possible, many a prediction would have said the same thing about Wii vs. PS3.

I guess:

3DS - 75 M
PS4 - 110 M
Xbox One - 55 M
Switch - 100 M

3DS - 75M
PS4 - 109M
XBOX ONE - 70M
SWITCH - 90M

3ds: 70m
Ps4: 100m
XB1: 60m
Switch: 75m

3DS - 75 m
PS4 - 115 m
Xbone - 55 m
Switch - 85 m

To be honest, I knew the 360 nor the PS3 wouldn't catch the Wii. Even after the decline of the Wii. They still did wonderful though.

No I don't think it will sell as much as PS4. I'm not mathematical (if there's such a word) with these type of things. I'm just a console owner of all consoles that paid attention to the trend. The Xbox One can possibly sell on par with PS4 in the US. Negative everywhere else though. I guess looking at our convo, I realized that maybe my prediction is a bit too optimistic. For the Xbox One I mean.

Results table updated to this post.