[ps2]it will be extremely hard to ever beat that imo dont know if any console will ever sell like that.
I can see it happening, indeed I would be surprised if it doesn't happen sooner than later. 155 million is the number many look at here for sales volumes but there are higher estimates (less than 10% though).
By various markets opening up and countries gaining if not wealth then people with some disposable income (a game console takes you out of a bad situation into something fun so it ends up surprisingly high on the list) it means there are plenty more markets coming online (China, South America, India, middle east perhaps, Russia maybe) and 150 million + is quite reasonable there. Japan might also be fading a bit as a result of that, though the death of Japan centric gaming might be harder to quantify if we are going to consider China and its state in the world).
Also at this point it is fairly reasonable to have had people that are now grandparents into gaming their entire lives (it has been about 40 years since the Atari dropped -- if you were 10 when it dropped or even a greasy teenager you will be in your 50s or nearer than not) so it has gone widespread/mainstream as part of that, though I will note it took a while longer for it to become a mainstream hobby (something some put at the feet of the PS1*), never mind it getting to the point where it is somewhat weird if you don't play games, so we also have that to look forward to. That alone will probably be enough but I will ponder further.
*at what time the PS1 really hit I don't know but I don't imagine anybody is going to put it much later than the January 1997 launch of Final Fantasy 7 (22 years ago, and nearer to 23, at time of writing, if you were 10 for that launch then chances are you have a kid or two, quite possibly one that themselves is now 10 years old).
So between all that and people often buying multiple consoles (bedrooms, front rooms and possibly a game room, as well as if they serve as media players) you surely have the potential to get there.
I am not entirely sure what the next one will look like. Probably going to be some actually useful multimedia device ("smart" TVs have had how many years now, would have been trivial to sort at basically any point during that and still utterly suck... we can probably count on that continuing for a little bit, to say nothing of TV replacement rates being far lower than that and 3d and 4k and whatever all floundering), and maybe for the would be competition to fail or render themselves secondary devices like the Wii (nobody sensible got the Wii to stay current on games). Speaking of failure wind in a bit of a failure that necessitates replacement (quite possible with the amount of heat modern things generate) and maybe a mid tier upgrade (if nothing else ensuring those two+ device houses) will pump those numbers up a bit, just make sure they have a few hundred hours of pleasure first. I am not sure what online will factor into this but will likely help if local play is to remain on life support. Phones/tablets might trouble this but they also have had many years and are still largely bad for what we typically expect from consoles despite outpowering many things throughout it, though I would be less surprised to see some company break away from Apple's awful design philosophy.
On the negatives then I don't know what effects the fractured culture (as in back when I were a lad there were 3 channels on TV, not that many more radio stations of relevance and a cinema with more than 5 screens was a shock) will do as far as being able to have some kind of cultural touchstone moment that drives a sale or three. On the flip side someone might marry wallet bothering gameplay with a reasonable loop that gets many people on side.
Edit
Do these sales milestones even mean anything anymore?
Yes and no.
Yes in as much as it gives an idea of install base as we are still suffering the idea of both exclusive games and games that won't work on multiple systems (I can buy a DVD and region issues aside...).
No as in the market is rather different to what it was before (see the earlier parts of this replay for at least a jumping off point there) and I don't know what comparing to original xbox sales really tells me. I have previously contemplated some kind of inflation adjustment type metric but did not get far.
For the most part it is a statement for fanboys and investors in Sony or those looking to fund games for their systems. For the man on the street I would probably say as long as the sales are not so low as to see devs pull out (see Wii U, or in some ways more interestingly the Xbox family and Japan**) then it is probably more important to find a controller that fits you, a form factor you like and functions you care for, as well as maybe any "I really want this game but it is an exclusive anyway for no real reason" type efforts.
**The 360 did see some very nice things as far as shmups that the PS3 (and in many cases even the PC) did not but at the same time it missed a bunch of fluff RPGs (
https://gbatemp.net/threads/ps3-and-360-exclusives-a-discussion.360416/ , give or take NIS' last minute efforts and Ni No Kuni).