360 will have a longer life than the original Xbox.  Third parties and Microsoft have already stated it would have at least a 5 year life cycle but more likely it'll be six or seven as it will become profitable in it's later years.

Nintendo will not be the first to make the jump. They're going to make the Wii last as long as possible.

Sony will not be the first to make the jump. They're obsessed with their "10-year plan" and won't jump until the other companies prove it has to if it wants to survive.

Microsoft will be the first to make the jump. They jumped first this time around, and while they will have a long shelf life, they will have the most reason to take the leap.

Next-gen will start around 2011. This is unless the Wii takes a nosedive in 2008-2009 due to weaker hardware causing some sort of unintendend lower sales (as I believe it will).

Should that be the case, I think Nintendo could first strike in late 2010, or early 2011.

If that doesn't happen, MS will most likely have the next Xbox out (provided they made a profit on the X360), in 2011 or early 2012.

Next gen should start around 2011 - 5 years from the last current-gen system made, and 6 years from the earliest. That doesn't mean every manufacturer will have a new system out by then. If anything, it could last an extra year due to the great specifications of the X360 and PS3 taking longer than normal to get all their juices out.

Why are people even thinking about next gen? This generation just started...

i was considering skipping this gen and then maybe getting a next gen console [probably nintendo] as my last, to keep until it broke.
the Wii intrigued me though... and i could still play gc games, and download vc, so i only need 1 console at my tv [i never had 2 set up at once, prefering to pack away the console i wasnt using]
well, i only need one except for the n64 games i still have and therefore refuse to pay £7 for.

i think i might keep the Wii until about 1/2 to 3/4 way into next gen [when for next gen stuff its still easy to find games, cheaper, and i know which games to get]... then buy my last console. [and maybe for the first time a handheld to go with it]

"next gen starts when we say it does", sony 2011

Hopefully Sony can actually have a full "10 year-plan" that actually finishes for once PS1 about 7 years and PS2 7 years so far but that will when it starts pushing 9years and starts to look REALLY old.
When the X360 came out i thought its just an upgrade of the Xbox(which i have) and it had no interest to me at all and was waiting for PS3 info and stuff and had a bad experience with Xbox(lack of games,controller uncomfortable,etc).At the "end" of last gen(it hasnt really ended yet the PS2 as life left) i wasnt ready for this gen it came too fast 7 years of PS2 isnt enough FFXII had just been released over here(UK) and i was about half way through and then the PS3 came and i was like ok i want it but i could have waited another year easily.
Nintendo doesnt need to push for next gen.......ever if sales continue.
MS needs to push for next gen because they will continue to sink the money into the industry until they make a profit and i personally think they are going about the industry the wrong way.
NextGen starts(i hope):2015
NextGen will probably start(due to MS):2012

I highly doubt that something like this will happen. A recent study that was posted here showed that the majority of 360 and PS3 owners were not even aware of their consoles' high-definition capabilities. It's all about the games.

I agree with your speculation that this generation might last an extra year. Sony is certainly off to a much slower start than they have been in the past, and they would benefit from another year of good software sales at the end of the PS3's life to pay for the manufacturing costs of the console. 360 will become profitable next year, but MS's games division has a ginormous hole of red ink to dig themselves out of. They'll want to milk the 360 for all it's worth while they can.

I don't know what Nintendo will end up doing. No one ever knows what Nintendo will end up doing. :)

One possibility for Nintendo is that even if Wii sales don't take a nosedive, they might still launch a successor a year ahead of Sony and MS.  The Wii will never be unprofitable for Nintendo, so they have nothing to lose by launching earlier.  If they start from an advantageous market position, as Sony did with the original Playstation, and launch early, again as Sony did with PS2, they could get a sizable lead over their competitors in both install base and developer support.  Remember how developers were unsure about supporting the Wii, and its runaway success has caused them to shift their resources?  Imagine if the next Wii launches first with their support already in place.

I'm waiting for HDD Tv.  It's got better resolution then real life.