Just asking because I've seen this argument coming up a lot.  Personally I think it ends when every console has sold its final piece of hardware.  In this way I think the 6th gen is still active but with only 1 player now.  Also the 7th gen won't end until 2017 or so most likely.  I just can't discount the 50+m consoles PS2 has sold and all the SNESs that sold after its gen was over.  If you can stay in the consumer eye longer and keep selling you deserve to have that counted.  It shows that your product had more longevity in consumer interest than the competition if it keeps selling even after successors are out.

When the majority of game releases move on to next gen.

When no more consoles are being sold.

If Gen 6 ended when all Gen 7 consoles were on the market, then the PS2 has only sold ~ 110 Million.

We know that to be false.

Depends on who you ask, I suppose. It's not like this is a real thing. It's a made up classification that means a lot less than some people believe.

Personally, I just don't care enough to argue about it. I just see it as a very basic timeline. It's too artificial to get worked up over.

when all 3 consoles are out

The problem is people aren't considering that generations overlap.

A particular generation isn't over until all the consoles are discontinued.

Marketing wise it should be when the MARKET says so. A product by itself, or the company that markets it doesn't decide when a "new generation" starts, it must first take a good hold of the market and make its presence be reckoned with.

I always take the 3DO as an example. It launched at the end of 93. It didn't sell from the start, it failed. Did the 3DO start a new gen? The 16-bit gen was still in its prime, nobody even noticed the 3DO, history can go ahead and lump it with the rest of the 5th gen (Saturn, PSone, N64), but the truth is the 5th generation didn't start until the PlayStation launched successfully *AND* established a solid installed base relative to all previous successful consoles and the whole market, and everything pointed to the consumers (and developing studios as well) moving into it.

So, to answer the OP question : Wii U hasn't started anything as it's been unabled to outsell the current-gen in any period of time consistently. It's the Wii U "next-gen"? Market wise? it'll have to earn its place in the market first, as of now it doesn't have next-gen games (only cross-gen, which don't really count), so it's pretty much a current-gen console until it proves otherwise.

A generation is when each manufacturer releases a new system. If one of them releases a new system even a year latter. Its not part oft same gen. So its pretty much over the same day its the manufacturer releases their console.

Now im pretty sure you are asking when do we declare a winner? Well its obvious that each sale counts no matter when its occurs

when sony says so

Damnit!!! That's exactly what I was going to say!!