Activisions CEO Robert Kotick predicts a long life cycle for the current generation.
link.
Define "long." Using US dates:
Xbox to 360 = 4 years (2001, 2005)
PS2 to PS3 = 6 years (2000, 2006)
GCN to Wii = 5 years (2001, 2006)
PS1 to PS2 = 5 years (1995, 2000)
N64 to GCN = 5 years (1996, 2001)
Saturn to Dreamcast = 4 years (1995, 1999)
SNES to N64 = 5 years (1991, 1996)
Genesis to Saturn = 6 years (1989, 1995; Sega CD and 32-X in there too though)
NES to SNES = 6 years (1985, 1991)
Master System to Genesis = 3 years (1986, 1989)
Of course you have a number of variables in there (divergent Japanese release dates, various other competitors, massive shortfall in shipping units, strategic surprise releases/blunders, etc), but in the end 4-6 years is typical with a number of market leaders tendering toward the longer span (i.e. if you are making money why slow up the gravy train and compete against yourself?)
With Moore's law slowing slightly (non-Intel companies seem to be having a harder time with this), design complexity increasing, diminishing returns in some areas, questions about future process reductions, basic design hurdles (how to get GB's off of a slow disk to memory for example), and so forth who is expecting a console from MS, Sony, or Nintendo in 2010? That would leave this and next holiday and BOOM! A new console.
And Activision has a point: why would publishers even support a new console right now? They are trying to recoup their current investments. Of course that is the very reason some would jump (if they feel it gives them a better position than the current hardware does... the same reason one of the big 3 may jump early with a new console as well). But are any of the console makers willing to ship without the support of the likes of EA and Activision?
I have been writing 2011-2012 for a while for this very reason: to get a design that will compell consumers to purchase as well as get developer support for 2010 seems nearly impossibly right now, especially with the market still gaining momentum. When total annual sales of consoles level or slow is when I would expect someone to jump.. unless someone is feeling a pinch and feels strategically ($) their best outlook is to jump early and invest losses in a fresh start.
Every generation is a gamble, but with process difficulties looking to get more difficult, and expensive, down the road a mistep in regards to design and partners could be very hurtful. It also makes it seem likely the N6/PS4/X3 consoles could be around even longer.