Yes, if PS4 sells well in China

The PS2 was a special case when it came to console sales, so I will say no!

I do't think the PS4 will have the legs PS2 and PS3 had. In the PS2-era Sony reached a lot new markets and the PS2 was still a great and cheap option after the release of the PS3, as the PS3 was too expensive. And the PS3 was initially too expensive.

I might be surprised though, China is a chance here for a growing market. Maybe also something else happens.

Pretty much this.

Also, this generation will probably be much shorter than the last one (5 years, 6 years tops) as their hardware power is too weak to keep up with PC graphics which is why most games are locked at 30fps while often not running in 1080p.

The PS2 had a second life in third world and emerging countries, where it often was the first and only console available. I don't think the PS4 can reinitiate that success.

The PS2 also had a huge success with casual players due to Singstar and Buzz. As often said about the Wii/Wii U, that crowd is pretty much gone by now.

Long story short, I do think the PS4 can beat it's predecessor but will already struggle hard with the PS1/Wii numbers and the PS2 is really out of reach.

To sell over 155m!?

I don't think so, but definitely will pass 100m.

PlayStation:

4 months (one territory) – March 31st, 1995 – 0.85 million
10 months – September 30th, 1995 – 1.77 million
16 months – March 31st, 1996 – 4.26 million
22 months – September 30th, 1996 – 8.07 million
28 months – March 31st, 1997 – 13.50 million

PS2:

1 month (one territory) – March 31st, 2000 – 1.41 million
7 months (one territory) – September 30th, 2000 – 3.52 million
13 months – March 31st, 2001 – 10.61 million
19 months – September 30th, 2001 – 19.58 million
22 months – December 30th, 2001 – 24.99 million

PS3:

1 month – December 31st, 2006 – 1.7 million
4 months – March 31st, 2007 – 3.5 million
7 months – June 30th, 2007 – 4.2 million
10 months – September 30th, 2007 – 5.5 million
13 months – December 31st, 2007 – 10.4 million

PS4:

1 day – November 16th, 2013 – 1 million
2 weeks – December 1st, 2013 – 2.1 million
1 month – December 28th, 2013 – 4.2 million
3 months – February 8th, 2014 – 5.3 million

PS4 had an excellent start, but we need to know a longer term trend to tell. Power whores say 8th gen consoles are too underpowered to be able to enjoy a long life, but PS2 was even more underpowered if we accept this stretched argument: my 2nd PC (the first I assembled personally), built buying parts between Nov 2000 and Jan 2001 was mid-low-end with a Duron 650, 128MB RAM and a 32MB GeForce II MX, while PS4 specs compare a lot more favourably with current mid-range PCs, particularly about RAM size and RAM tech. If I'll build my next PC this year I'll play safe equipping it with 16GB, but even so, it would exceed PS4 RAM by 2:1, not 4:1 like my 2001 PC did with PS2 RAM, and for many years I'd use that extra RAM not for games needs, but for other uses like graphics editing and video conversion, excessive multi-tab web browsing and to make up for the larger size of Windows compared to specialised console OS, while most games, typically run on PC with as few other programs open as possible, will just need 8GB machines for a long time, so even ports from PC games shouldn't suffer excessively, except about graphics comparison with high-end PCs, just like it happens every gen. So we can't tell yet anyway, as HW power isn't the sole factor, but the underpowered argument to deny the possibility is invalid IMVHO.

As time has gone on games have been selling ever greater percentages of their total sales within the first week.  The same is showing true for just about evey other electronics launch including iPhones and peripherals as well.  So in addition to this mentality, there is also the fact that last gen lasted WAY too long and so people have been chomping at the bit for something new.  Expect sales to drop off quicker than usual after the first 2-3 years.

Sony doesn't want another 8 year gen anyways - bad for business.

I think Xbox has taken way too much of the US market for that to happen. Add to that the fact that Japan is massively down, and it seems very unlikely.

I think so but it depends on how well it does in the developing markets. Longevity is key