In my opinion this is a little too hard to predict at the moment ...

This is not meant to be an overly accurate chart, but if you use the XBox 360/PS3's processing power as being 1X then this is what I expect you'd be able to sell a system for with relative processing power in a given year:

Depending on the strategy the companies choose to go forward with will largely determine what year they release in; if Sony and Microsoft really want to push the boundries on graphical improvements they will need to get into the 16X to 32X range, which will require either a later release date or a higher price tag.

In my opinion Nintendo has a massive advantage over Sony and Microsoft. In 2011 Nintendo can release a system which is dramatically more impressive than the Wii (noticeably better than the XBox 360 and PS3) at a price which is similar to what the PS3 and XBox 360 will be charging at the time. To a certain extent this puts Microsoft and Sony in a tough position because they can either stick to a modest upgrade, they wait and give Nintendo an opportunity to build a solid userbase, or they produce an expensive system; the modest upgrade can work if you supply an alternative reason to upgrade, waiting can work if Nintendo fails to use the first mover advantage, and having an expensive system can work if you provide adequate reason to pay extra money.

At the moment I would expect the XBox 360 to release a moderately powerful (8x to 16x) system in 2011 for $400 to $500, Nintendo to produce a less powerful system (4x to 8x) system in 2011 for $200 to $300 and Sony to hold out until 2012 or 2013 at sell a high powered (16X to 32X)  system for $400 to $600. I expect the XBox 360 will die soon after the release of Microsoft's follow-up system, the Wii will sell well for a couple of years after Nintendo releases a follow up system due to its low price ($75) and the PS3 will be on life support after Nintendo and Microsoft release their systems.

PSP 2 for the handhelds Wii 2 with motion sensing and better graphics but not until the price would be like 300 $

My guess is: MS - 2011 Nintendo - 2011 Sony - ?????? Huge question mark here depending on how the PS3 fares in 2008.

MS>N>Sony Microsoft will probably jump the gun. Again. Nintendo has the weakest hardware out of the three and so will need to update. Sony cant afford to be the first, the ps3 is screwing them over financially.

I have to agree with davygee's sequance and for the most part with his dates. 

Microsoft - They will want to be the "First ones out of the gate".  They probably would like to have a 5 year lifecycle for the 360 to recoup some of the losses at the begining of the cycle. That would put the 720 at about 2011.  But if the Wii begins to get to big a lead in market share, Microsoft will probable release the 720 in 4 years to counter the Wii sales.

Nintendo - Nintendo will not release a new console while the Wii is outselling the compition.  Why would they want to invest in a new console when they are makeing huge amounts of money on the current console.  Expect the Wii 2 to be released 6 months to a year after.  Nintendo will probably wait until the 720 is outselling the Wii by a consistent 2:1 ratio before they will release the Wii 2.

Sony - Because of the massive losses Sony has taken from the PS3 console, Sony will probably have to extend the consoles life cycle as long as possible to try to recoup as much as they can on the PS3.  I expect them to skip the next generation of console and stick with the PS3.  They will have to give up marketshare to return to profitability.  Expect them to be the first out with a new console in the generation after that. (maybe 3 to 4 years after the 720 is released)  I expect that they will learn from their mistakes and have a much stronger console then.

*The pridictions for Sony assume that the gameing division survives this generation.  It is not dead yet, but if Sony doesn't make some serious changes soon, that division may end up being closed.

P.S. Please be kind to me as this is my first post.

Man tough question. This depends on so many factors. But if PS3 continues to not sale and continues to cost Sony billions then PS4 will be the first console out and PS3 will be shut down. There is a very strong possibility that PS3 will die before PS2. But here's how it'll work if this is the case. PS3 will go into 2008 still saling how do I say pathetically. Sony will soon attempt to drop price to hopefully entise gamers but over this time they had lost most of their exclusives and dev support and it wasn't going to matter anyways. Now they have a console losing even more money. But this time they could have lost upwards to $4 billion if not higher. Thus if it doesn't start to sale Sony will soon have to discontinue the product and admit a failure. Now the reason Sony would have to do this and not MS like last generation and this is because Sony is just not as big of a corporation as MS. Sony expects to make profits off their Playstation brand. And with PSP a failure if PS3 falls similar ways, we could see a cheaper version of the PS3 on both Sony and consumer by as early as 2009. And we could see a PS4 as early as 2010 to 2011. We'd see them take a similar approach to what the X360 did. Now if MS comes in last there are some pretty strong chances they'll be gone which would leave just Sony and NIntendo for the 8th generation. They'd probably release around the exact same time in 2011-2012 timeframe. If Nintendo lost then I'd expect them to start off early as well but along with MS too as if NIntendo loses Sony is going to win. There is nothing MS can do right now to prevent Sony from winning. It's in Sony's and NIntendo's hands really. Now if Nintendo wins by a landslide some think Nintendo will let out an entire new console, N6, to replace the Wii with more powerful hardware plus an even more innovative controller. Some are thinking as early as 2009-2010. Now Wii would have power to control this if it gained in these 3 years upwards of 60 million buyers. But I don't see NIntendo playing it like that if htye are still making money and saling systems. My best bet is Nintendo has some things up their sleeves to make the Wii very long term. But we'll see. But that's my guesses.