Both the Gamecube and the N64 were given a 5 year cycle and they were seen as moderate successes whilst the original Wii was a huge success and was given 6 years. The way the Wii U is going it will probably match the Gamecube sales at best so we should see a follow up in 2017(5 years after the Wii U launch). Sales have been abysmal for the Wii U, I can't see Nintendo being content with 45,000(outside holiday season and the occasional big title) units a week worldwide for another 3-4 years.

it might because Iwata mentioned that they'll unveil further details on NX.

Most ppl and I also agree that '16/17 will be the HH/HC release dates, but the counter argument now is did Nintendo buy some time with their new mobile business?  Despite industry rhetoric, its safe to expect PS5/XB2 in '19, so even if Ninty's (rushed) plan get pushed back a yr, they still get a 1 yr head start on their competition and extra time to get the HW / SW right & ready.  

Again I stand firmly behind 16/17 as the release dates for NX hw, but won't be surprised anymore if they push it back to 17/18 thanks to mobile $$$ keeping them afloat.

Why?

there is no way Wii U will be the focus of e3 next year. That makes no sense, why even talk about NX now if that was the case? I see there are still some people who think that Wii U can turn around but maybe im looking too deep into things

5 years for both 3ds and wii u. not too late nor too soon.