What I'm really wondering is did anyone actually think their answers out? If Nintendo released the DSi and intended it to be the next generation don't you think they would have advertised it as such? I'm sure Nintendo could have raked in a hell of a lot more sales if they were saying DSi is the new wave in handheld gaming to put all the others to rest instead of saying the new iteration of DS. Hmm obviously Nintendo still thinks it is part of the DS series and they show that in their financial reports. Thus every respectable site keeps it that way.
The point you are all missing is "next generation" is MARKETING not a bar line. Anything can be marketed as anything. You can argue technicalities that don't exist about generational differences all you want but the people that decide in gaming when the generation changes is Microsoft, Nintendo, and Sony. And trust me they will not hesitate to tell you they have a next generation console coming out because they know they can generate more hype with that than the latest iteration.
We don't decide when a generation begins or ends. Sony could release a PS3 that is 2x more power than the current PS3 and if they still group it as a PS3 then it is simply a new iteration. Sure we can discuss technicalities but they amount to nothing. Because we all know that if they had intended it to be the next big thing they would have advertised it as such. Next generation is really just marketing.