When does a generation end?

[F0X]

VGKing said:

Next-Generation starts when there is competition.

For example with the handhelds, next-gen didn't truly start until the Vita launched.

A generation is defined by a bunch of competing products. If there is no competition, there is no new generation. If Sony and Microsoft were to let Wii U have 2 years on the market we could consider the Wii U an extension of 7th generation instead of part of the 8th.

Just my opinion, I'm sure many will disagree.

That's fine, but this is a thread about how a generation ends, not starts.