PS2 can hit 200m if Sony release PS2 Classic with 2TB hard drive crammed with PS2 library for 49.99$

The only way that could happen is if say MS dropped out of the console business and their  base went to PS , even then you would still come up short , PS360 combined fell around 30 million short, you would need something like china opening up fully to games and that's not happening.

It depends. If a company decides to make a family of upgradable consoles, then yes, it may be possible. Otherwise, no.

It will not hit 150m, let alone 200m.

Ps4? No. Some other console in the future? Probably not. While generations are selling more over the last gen typically, dedicated consoles won't be around in 20 years for gaming to become big enough to sell 200 million consoles to a single manufacturer.

Mathematically speaking, it should be inevitable due to the ever-increase in population. However, based on that alone, we haven't seen the logical increase from one generation to another. The cause of this might not have anything to do with the console market itself, but with other factors such as the current economy and how the new generation is encountering difficulty in finding stable homes ( therefore they will not commit to buying non-essentials such as a console, at least not brand new ).
Also, even if the population is increasing, it doesn't necessarily mean there are more families, but rather a bigger size average in families, and family members tend to share a single console. It's really hard to pin-point what would need to be done for consoles to reach new heights, honestly.

Yes, that's a good thought.

I know that the easy and short answer for the question is no and not in a foreseeable future.

But, the thing is, there are still many parts of the world that aren't playing current gen consoles and the console industry isn't trying to explore different sorts of sku's with different prices.

Besides, after 2 decades of gaming (let's say since PS1 release, when the market really took off) I guess it's time for the market to grow with the youngsters and a new generation of gamers, or is it too soon?

When will the sons and daughters of the NES generation will move to their own homes and buy their own consoles? The worldwide console family has to grow someday, right?

Good thought, but why do you think so?

Since PCs/notebooks became ubiquitous, consumers are buying more and more dedicated devices like tablets, smart stuff, internet of things. Why would people stop buying consoles? Do you think the industry will want to move fully to digital streaming of sorts?

Great thoughts. I've seen some people I met saying - I just play 5 games a year, I'm not buying a console, I need to save more.

On the other hand, I've seen many end up buying a console when it gets cheap down the road. Consoles aren't that expensive. When it hits $300, it's not like the middle class and even the working class just can't get one for Christmas. So, even though the economy has been tough for many that are trying to leave parent's house, it still puzzles me why such families wouldn't invest on a console.

There's one thing though, related to this, which is having a child. I guess once you've got children, the decision on buying a console is easier, but as we said youngsters are kind of struggling to leave parent's home let alone having children.

Me either. Although handhelds like NSW and 3DS as the get cheap has a lot of potential to sell more than one per family, I still believe that the ship has gone since smartphones mass adoption. 2DS is out there and it's not changing things for 3DS family.