When looking at power x price, things could go like this: wii u was released in 2012 for $299/$349. It has about 3x the raw power of ps360 and it's controller is somewhat more expensive than a regular controller, it also had 4x the amount of ram memory. the ps360 used top tech from 2005/2006, so wii u had to use gpu tech from at least 2008-2009 to be 3x more powerfull.
If a wii u successor releases in 2017, this has to be considered: ps4 (most powrfull home console of 8th gen) didn't come close to using top tech of 2013. this means wii u successor can use tech from 2013 and still be 4-5x more powerfull than ps4. since it won't have to use tech from years later, this part of the hardware will be proportionally cheaper than wii u. we should probably/hopefully see a controller that's a fusion of wii mote + nunchuck and the pro controller, so this part of the hardware will also be cheaper. ram memory is getting stagnant, a top pc from 2015 barely has double the amount of ram of a top pc from 2010-2011. So I don't see any 9th gen console having more than 24gb of ram (even 20gb might be too much). let's say it will have 16gb of ram, so it's also proportionally cheaper than wii u. a 100-200gb hard drive/flash memory might be the same price as the current 32gb on wii u, so this part should stay the same price.
with all that considered, wii u's successor could be released for $249 in 2017, having 4-5x the raw power of ps4 and 2-3x it's ram memory. or nintendo could make something 6-7x more powerfull than ps4 and sell it for $299 or a little more. still in the same price range of wii u at lauch, but with a bigger jump from the previous generation.
