Once it sells for less than it costs to manufacture.

hopefully as soon as possible but i think middle 2008

So is it entirely possible for the PS3 to NOT have a 10 year plan (many say Sony is stupid, and the next gen will be in 5 years)....seeing how UNINTENTIONALLY, the PS2 may last that long.

But at the topic, it'll stop selling when they stop production.....even by 2009 when the PS3 library is great, and all support has shifted from PS2 to it, there's still a 5000+ library of games to play, and unless there are no more PS2s being made, then they will still sell

Hopefully soon, so that Sony can move some of those sales to the PS3. I predict late 2008.

 There is nothing unintentional about the PS2's longevity.  It is the success of the PS2 that has made Sony proclaim that the PS3 will be a viable format for ten years.  It is the crux of Sony's woes: hubris.  Like a world class fighter who has dominated the ring for so long, they strutted and flexed, letting everyone see how mighty they were.  Of course, some scrappy kid (or old man) entered the ring and knocked Sony out in the first round and now they get up with glassy eyes and stars over their heads still posing for the cameras and holding their hands high while the ref checks to see if they haven't suffered major head trauma.  

Sony knows the PS2 is selling.  The PS2 is still funding the future of the PS3 and Blu-Ray.  I think they will continue PS2 production until there's no milk left in the cow.  Especially considering that Sony has removed backwards compatibility from the PS3 I wouldn't be surprised to see the PS2 always in contention this generation.  If it's at 120 million right now...don't be surprised to see it hit 135-140. 

I sold most of my PS2 games when PS3 came around because I was so impressed by the PS3 games, but now there are some classics that I want to go back to, and even some PS1 games that I missed out on (FF VII) and that would be nearly enough for me to buy a cheap PS2, but luckily enough I have kept mine. I would expect the used PS2 market to continue past 2010, but I suspect new PS2 sales will be over 2009. Software sales are lacking, and they will dry up soon. However, I think it will continue to support PS3 until late next year, and then the PS2 can get a price drop to keep its sales up

2011

PS2 will make it to atleast 130M sold to consumers.

 lol....who does this?  How much can you honestly get from EBGames or Gamestop for PS2 games?  It's not even worth driving to the store.  Not to mention the fact that you probably through away some amazing games just because you were wowed by better graphics.  Did you sell your GTA collection, too?

around 2010

It all about price. When the current systems reach sub 200 price levels expect the ps2 sales to zero out.