The xbox 360 came out 5 and a bit years ago, not 3 years ago
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consoles, at best, should last 5 years as a primary development platform, as the tech available is now about 12-16 times more powerful for graphics cards. I've no problem with an individual console being supported, look at the ps2. But as a platform designed to be 'the cutting edge', the current consoles are too old and too decrepid.
It's not the tech that irritates me as much as the ignorant users who sit their blatantly believing that 'new tech wouldn't make games better', or even significantly. I propose that anyone here in such a mindset go and pick up san andreas, or any last gen game on the ps2/xbox and put it in their current gen console for comparison. See that difference (not only in graphics but in gameplay enabled)? The difference to current consoles and the tech available is easily that gulf and then some.
Finally, the market is definitely there (and is, in fact, huge). Plenty of sheep went out to buy the new xbox 360 slim to replace their old xbox's just because they were 'new'. The market for a new console is bigger than what we had in 2005, so there's no reason to delay another. It's just because the console manufacturers can get away with it to cash in more.
Why can they get away with it? because people continue to buy the shovelware put out by lazy developers and publishers, so why do they need to change? It'd be like scrapping the x-factor, it's terrible and mind boggling bad but still popular as it's 'safe'. CoD: Black ops was the biggest mockery of console gaming i've ever seen and, here's the best thing, the playerbase lapped it up. A best seller with no notable changes and an overall worse game than a game that came 3 years previously. It's appalling. Then companies like activision have the balls to blame platforms like the PC of having 'piracy' for the reason for reduced sales, and not the fact that their game is sub-standard in every way. (It should be noted that crysis did deserve better sales, but it still sold very well for a game considered so demanding and with quite niche gameplay - people like safe, people like corridors dressed as the outside world, means they can't make mistakes and get lost).
Also, i find your comparison to a new console being equivalent to winning some kind of luck based prize perplexing. In fact, a new console i akin to already having the winning lottery ticket, but not being bothered to cash it in. The prize is their if you're willing to to put in the effort. If every console player this year decided that 'we're bored of tripe', and stopped buying the shovelware like CoD, we'd likely see a new console generation in 2012.