I think the 10 year cycle for the PS3 is a feasible thing.They are already into the second year of the system.But that doesnt mean there wont be a PS4 until 2016.Probably around 2012 there will be a new machine out.
Sure they can support it for 10 years if they really want to, but that doesn't make much difference if the last 4 years it sells 4, 3, 2, and 1 million (in fact that particular scenario makes  10 million difference, so not too bad I suppose, but it isn't going to get them anywhere near 150 million)

But the PS3 may kepp support until 2016 ,just as the PS2 is getting some support well into 2008 when it launched in 2000(if you count the years its 9 years no less).
The PS2 is 8 years and 5 months old (from Japanese launch)

The PS3 ,when it gets under the 250 price point ,will find many more users.Saying it wont ever reach the PS2 userbase is adventuring too much.
Yes I am sure it will get a boost wit a price cut, but that will not bring it anywhere near PS2 userbase, most people have already made their choice this generation.... Wii is clearly taking many of those who had a PS2 last gen.

About the PS4 well Sony cant let the same of this generation happen by giving MS a 1 headstart at bringing console that isnt too apart from the Sony one to the market.Sony should take one of these approaches:

1)Let MS take that 1 year start ,ok.But then ,one or two years later launch a Sony console vastly superior to the MS one and kill it instantly as all the hardcore gamers MS may have amassed make the jump fast to the Sony plattform. Is this some sort of admital that the PS3 is in fact not vastly supirior to the X360? after all that is what they supposedly did this generation, and while I am quite sure the PS3 will eventually pass X360, it hasn't exactly "killed it instantly" No Blu Ray advantage ,no free online ,no web browser and built in wifi advantages that only those who know will appreciate.I am talking about something so sensible in videgaming that it turns the X720 (or whatever is called) obsolete the same day it hits the market.Until then ,refine the PS3 price and library until they reach their highest and try to get ports of the games that arrive to the market even if its a dumbed down version. You didn't seem to explain what this thing was that will make X720 obsolete... do you mean they have to wait until MS releases it, and then set about working on something that would make it obsolete? because It seems an odd strategy considering the research and development involved into making a vastly superior version of whatever magical thing makes the X720 appealing, would take a good amount of time (probably longer than 2 years) which would then of course just give the X720 an even longer time on the market with no (Sony based) competition.

2)Develop the PS4 right now and be ready for whenever MS announces their machine announcing theirs in the next monts.This shouldnt be that difficult,the Cell architecture is gaining popularity between developers and is fully scalable ,the BR is already developed and could include de 8 layers version at 12X ,the PSN will be fully portable to the new machine ,and their have their contract for Nvidia for succesive generations so Nvidia could provide with the best graphics card at the moment.For Sony launching a PSN enabled ,blu ray 200Gb 12X ,Nvidia-built graphics card ,and Cell powered motherboard with say 7 or 8 Cell or Cell+ at 4200 mhz,full BC with PS1-PS2-PS3 catalogue ,everything along 4Gb of Ram and a monster HDD should be a breeze.The problem was to develop the PS3 ,but that effort will pay off in the future.It will be a monster machine and with technologies alredy mastered by developers and proved in the market ,that wont be nearly as expensive then. I actually can't think of anything to say to this paragraph..... perhaps "Oh I see, you think they are going to tape 2 PS3s together"

Please stop trolling. Why would PS3 support crash in Q1 2009? Because the developers will go to the Wii? In that case 360 support would drop even more. And how can you know on which platforms the next-gen multiplat games will be?

PS3 support will crash in Q1 '09 because there's no major third-party PS3 exclusives outside of FF Versus XIII announced for it after that. All of those PS360 action games and FPS's we're seeing announced for TBA '09? A large number of them are former PS3 exclusives that developers took multiplatform in order to cut their losses. I'm willing to bet that a lot of them will be canceled or shoved out the door in an unfinished state as well between then and now.

Just look at the number of third-party exclusives announced for the PS3, 360, and Wii thus far in 2008. The Wii netted a bunch; the 360 got a couple of games from Square thanks to their "partnership," as well as a few other games that they threw a boatload of money at; and the PS3 got... well... nothing notable, that I can think of. The tide has already shifted toward the Wii, but it probably won't be until next year that we see the full effects.

For further proof, look at the fact that PS3 fans continually list vaporware like Kurayami and Ni-Oh in their "PS3 exclusives" lists.

Also, the accusation of "trolling" has to be the most overused thing on the forums right now.