Oh, such irony!

However its hard to say what will happen.

Intresting thread. However I see three (fictional) scenarios how the PS3 could reach a 10 year life.

1st Scenario: There will be no PS4. The PS3 will be Sonys last console. But it will last 10 years. (Maybe even longer.)

2nd Scenario: There will be a PS4 with no backward-compatibility. The PS3 will still be sold to play PS3-Games with it.

3rd scenario: Sony will not release a new console, but upgrade the PS3 with firmware updates and additional motion controllers into a PS3.5.

You forgot the most likely scenario:

The PS4 will essentially be a faster PS3 (faster CPU and GPU & extra memory) with motion controls and perfect backwards compatibility that will be called PS4 but essentially be what the Wii is to the GC...

So just curious, what happens when/if Microsoft releases XBox 720 in 2011 lets say that is considerably more powerful/ feature rich than the PS3?

What works for Nintendo usually doesn't work for everyone, so it's hard to really look at them and try to copy what they're doing.

^ I doubt MS or Sony will make a big jump in the pwer of their next console. Only ninty will move to HD with their next console and that would only bring it on par with the current HD consoles.
Developers don't have time or moeny for more elaborate titles at the moment so a new control method that is better than the Wii's will be what the next gen will be about.
And don't forget, the high price of an ultra powerful 360 will be higher than that of the PS3.5 ...

I don't own a PS3, and probably never will, but I'm not sure I agree with the argument here. I think this generation has already thrown a lot of curveballs our way, and I don't think the PS3 is dead in the water here. I think the price cut later this year will re-invigorate sales and keep the console afloat, from which point people will jump on with the introduction of new software, etc. I think there's still a lot of goodwill toward the Playstation brand and I find it hard to believe that the PS3 will just fall flat like that.

      Of course Microsoft will make a big jump in power with their next console, otherwise there wouldn't be much reason to buy it.  As far as games goes Microsoft needs to have a console that can play games with graphics as close as possible to pc games the way that the 360 can play games like Bioshock and Fallout 3 in comparison to  pcs or they lose a big chunk of their market to pcs.  At the very least the next xbox will be able to run Crysis as well as current high end pcs do.

I have to wonder too ... would Sony fans be cool waiting around 4 or 5 years for Sony to catch Microsoft in tech? Potentially having bigger budget 3rd party projects bypass the PS3 entirely for instance. 

Nintendo fans put up with it, but a lot of them stuck with Nintendo through the N64 days (where you'd get sometimes 1 game literally every 2 months) and the GameCube days ... they are pretty fiercely loyal and Nintendo augmented that with the more casual shopper. 

I don't know if the same concept could work for Sony. They rely a lot on hardcore gamers ... if the PS3 is badly outclassed by an XBox 720, I think a lot of what's left of Sony's fanbase would jump ship. 

After spending 10 billion combined on the original and 360 MS finally posts a 500 million profit for it's Xbox brand last year. So you think they are in a rush to spend another 5 billion on a new console? Why would they do that when the Wii is already outselling the 360 2 to 1 even though the 360 is 2-3 times more powerful and cheaper?

The 720 is a fanboy pipe dream. You have no concept of how expensive a console would need to be in order to make a PS360 look "dated". 

I didn't forget this scenario. However this scenario would mean that the lifecycle of the PS3 would end as soon as the PS4 would emerge. Like the GC ended, when the Wii appeared. (Nice example ) Which means that the PS3 wouldn't have the 10 years lifecycle.

I only listed scenarios for the 10 year lifecycle.