2016, most likely.
Launching NEW 3DS next year won't be a problem. DSi XL launched in Europe and the US almost a year before 3DS arrived. So, not a problem there.

3DS is already going down in sales.
Nintendo can't afford losing it's main source of revenue: the handheld market.
The 3DS business already has a starting price of 99$ with 2DS. So a price cut won't really push sales of the console. That or Nintendo has a lot of exclusive content planned for NEW 3DS - which could make people rebuy the console and help sales.

But if that doesn't happen, they don't have a home console business to fall on when 3DS reall starts going down.
In 2016, the Wii U business will be in grave decline with Nintendo focusing on making games for the new generation of home console and handheld and no 3rd parties to cover their backs or a Wii like success that makes them earn a lot of money even during its last days.

Might aswell take what' s left of the handheld momentum they have by 2016 and carry it to a new generation.

Iwata actually basically already confirmed Fusion (HDS) for 2016:

http://www.neogaf.com/forum/showthread.php?t=818167

"Also, the idea I mentioned about redefining the definition of video game platforms will also require approximately two years."

Satoru Iwata - May 2014

The "redefinition" of gaming that he's talking about is the Fusion idea that he brought up in a previous investors statement, about Nintendo looking into a new setup similar to the iPhone/iPad/iPod touch (different devices that run the same apps with similar hardware).

New 3DS doesn't mean jack all, it's just Nintendo's usual last gasp redesign, in fact it's timing hints heavily that a true new Nintendo successor is imminent, case in point:

DSi XL (last DS revision) launched in Japan in November 2009
3DS launched in Japan in February 2011

(approximately 14 months later).

New 3DS launched in Japan in November 2014
15-18 months later = spring 2016 ... convienantly right in line with Iwata's above statement.  

I rather have Nintendo design and advertise the thing as if it were an smartphone, but with the capability to play console-like games on it. That's what I think woud be the best way stay relevant and have a growing following.

Nintendo also said this http://mynintendonews.com/2012/06/12/miyamoto-says-nintendo-is-working-on-3ds-successor-and-not-a-3ds-revision/

so what to believe :P I guess just wait and see

You have to look at that actual quote though, nowhere does Miyamoto say they weren't going to redesign the 3DS, just that he personally was happy with the design of the 3DS and that some kind of idea he had would be better served for a future handheld. 

Iwata's statement is clear and made to shareholders too, not an off hand comment to the press. 

LITERALLY just released the "New" 3DS. Give it at least 18 months

Announced this E3, i say, and then released in April 16.

It's big brother console will come Nov 16.

Nintendo LITERALLY announced the 3DS the same month they released the DSi XL in North America, lol. 

not before 2017.

why wouldn't nintendo's next handheld be hd? aren't most smartphones hd and we're talking about a new handheld that's coming in a few years.