All that next-generation talk makes little sense. First, you need to know one thing to start these kinds of discussions: what defines a new generation? Obviously, it's when a new videogame releases after a long time without "new" videogames, and when that new videogame improves the general graphical power when compared to old consoles. It has been like this since the NES was considered to be in a new generation, because, well, it was more powerful than a Atari 2600 and had been released a lot of time after 2600's release, and it actually never changed, no matter how anyone tries to spin that. Wii U was next-generation when it wasn't released yet simply because it is more powerful than the last gen consoles(PS3/360/Wii) and has been released a lot of time after the release of those consoles. It's current gen now, because it has already released and started a new generation based on new graphics and release dates. The power difference itself doesn't matter, what matters is that it exists, even if it is small or big, and that difference in power needs to exist with a difference in release dates to define a new generation.
