Possibly, but I'm not sure.

The Wii U will most likely be featured at E3 2016 as well, but I'm not sure whether the Wii U or NX will be the focus.

source please? because they never said if it was a handheld or a home console.

Don't tell me.

I'm not one of those believers. In fact, I think it would be a terrible idea.

Games. Metroid, f-zero, smt x fire emblem, true kirby, third party colaborations, new ips and smaller games (were you expecting something like splatoon/cap toad/kirby rainbou curse last year?). They have waht it takes to make 2016 at least comparable to 2015 for wii u. things can slow down in 2017, when a successor might be released.

2015 is the peak yr for Wii U, so with a mostly slow 2016 I think Nintendo will launch NX hh in Q4 '16 (5.5 yrs after 3DS), with NX home shortly after its E3 '17 focus, or Q2/3. I don't think Nintendo will treat their next home con. as its "own" console where it gets a traditional holiday launch, just a new member to the NX line of products.

The source is common sense and knowing how Nintendo operates.  

They said it was a dedicated game platform.

Doesn't matter if its handheld or home console, games still take 18-24 months of development time, launch titles sometimes require even more than because the developers need a longer planning period to figure out how to properly utilize new hardware. 

3DS development basically shut down Wii development after 2010, the only really big thing Nintendo released after that was Skyward Sword, all their dev teams shifted to 3DS development. 

Same thing with GameCube development, they had one Zelda game in development but after 2004, all of the other core EAD teams, Retro Studios, Intelligent Systems etc. stopped GameCube development to focus on the DS/Wii launches. EAD Tokyo as a new studio had DK Jungle Beat, but that was more like a experimental title I think designed to get the studio on its feet. 

I can see them announcing the NX at E3 2016 but still focusing on Wii U mostly games-wise. Then in 2017, NX will be the major focus, including games.

It's already the no.1 focus for them in their R&D/development studios. They're not going to repeat the 3DS/Wii U which had really poor launches. 

Good launches are not magically made the year the console releases, it's a result of great planning that takes place 2-3 years before the product launches. 

Nintendo failed the 3DS and Wii U launches because they were lazy/lax in their planning during the time period of 2008-2011. Those were the key years and that's where they needed to be sharp and weren't. 

I think they mistakenly thought they could just show up with two new gimmicks (3D screen and tablet controller) and people would go crazy over those just with Nintendogs and Nintendo Land (the new Wii Sports). 

They also have smart device development to think about now. 

There are many franchise that haven't been touched for Wii U as a Nintendo home console. The absence of Mario spin-offs is bothering me, Pokemon, and F-Zero, Punch-Out come to mind. They could also release a sequel for a franchise already released: 3D Mario, Kirby, Pikmin, DK... Same for 3DS: Pokemon Gen 7, the countless Pokemon spin-offs, 3D Mario, etc. Lastly, remakes/remasters and collections. And this is not counting any collaborations with 3rd parties.

I still think NX stands for two new platforms: A new handheld to be released in 2016 and a WiiU sucessor to come in 2017.