Hey guy !!! Nintendo Switch just confirm. So this rumor is true.

http://www.mcvuk.com/news/read/pok-mon-mario-and-zelda-headline-nx-dream-line-up/0170678

This is the rumor since 4th August 2016, according to this rumor

1. The same sources confirmed that the Eurogamer report last week - which revealed that NX will be a portable machine that can be plugged into a TV and features a breakaway controller
( This is correct !) ;)

2. NX is currently slated to launch in March next year worldwide.
(This is also correct !) ;)

3. Developer Game Freak will bring Pokémon to the platform, while Nintendo’s first party titles include the previously announced Zelda game – Breath of the Wild – and
a new Mario game. All three products are scheduled to appear within the first six months of the machine’s life.

So i believe this will correct as well , because "Nintendo have told MCV that the firm is determined that NX will not suffer the same slow start as either the Wii U or 3DS."

Follow the tradition of new Pokemon main game.
- Zorua and Zoroark reveal in CoroCoro February 2010 (beginning of gen 5)
- 3 starter and Legendary of XY reveal in trailer at 8 Jan 2013 (beginning of gen 6)
- Magearna reveal in CoroCoro February 2016 (begining of gen 7)

That is the reason why there is no 3rd legendary for Sun Moon. Pokemon movie 2017 will have Marshadow as mascot and feature Solgalio and Lunala. Pokemon movie 2018 will have mythical Pokemon from gen 8 .

If my theory is correct . February 2017 gamefreak will announce gen 8.
Slowest might be February 2018 for gen 8 announcement.