Let's assume that the successor will come out around late 2017 too.

6 times more powerful than the wiiU with same architecture

So 12GB RAM etc?

Yeaa! But I am looking more in the stronger GPU department than anything else...

faster than the PS4 by 25% or so.

similar to the wii u's relationship to last gen

I want it to have enough power to be under $250 again and to make better looking games than the PS4. If Nintendo somehow attracts a lot of third party next gen, than the power and price can be higher.

Too hard to say. Anyone saying it will be the same as Wii U's relationship to PS360 is simply basing it on the approach Nintendo took to Wii U. Since Wii U has done poorly thus far, I think it's safe to say that Nintendo will take a very different approach to the Wii U2, unless U1 does a complete turn around.

I expect Nintendo to go either the full on power route and build something that will compete directly with MS and Sony, or do something completely different and build a possibly weak platform that offers and unique experience. Something that works with mobile or handheld products as well. I'm hoping for full on power SNES/N64/GC style, but not holding my breath.

something same or higher than ps5 or xbox two.

and GPU still the best.

I have no idea, honestly. I think Nintendo is going for stronger hardware next time, but there's no real reason to why I think that. It depends on their way of thoughts for the next gen. Maybe they're going to allow the next Nintendo console to be a bit more expensive, which I think is unlikely, but still possible.

More powerful than a PS4 and X1 but not powerful enough to make a significant amount of people upgrade half way through a gen or powerful enough so that nintendo can claim they are next gen.