Maybe they will even repeat the same thing they did with Twilight Princess and release NX version earlier than WiiU's

If you look at other tech, such as the new iphone,you get a reveal just before the products release. Perhaps Nintendo's thinking that typical early console reveals is a tradition that no longer makes as much sense with the dramatic changes to media.

Again you dont need E3, Gamescom, Tokyo game show to show your console in order people to play, only very small number of people actuly goes to shows like those (we are talking only around tens of thousand of people, E3 had 50k visitors, and that's nothing), Nintendo will most likely team up with some huge retailers and moles where you can be able to play and try NX and that's far more effective for people because bigger number of people can try it, and we already saw Nintendo doing something similar before.

Rumours will be totally irrelevant moment Nintendo official reveal NX.

Thats fact, they done things you talking about with Wii U and 3DS and we all know how exactly Wii U revel and marketing was bad and misunderstood (IMO Wii Us single biggest problem), they now basically changing their strategy with revel and marketing and that's positive of course.

Perhaps there are fewer people, but most of them are journalists especially on E3, so they can write their previews, which if they are positive are actually great marketing. You don´t need to a game conference to show games, but it´s smart to do so, since they will get more media coverage on events than just reeleasing a trailer out into the blue. Sony unveiled PSVR at a conference and you can enlist for PSVR events in The Netherlands so there is no obvious reason not to both. Then you have both (positive)media coverage and previews and user experience and word to word advertising. 

I think NIntendo will hold some NX conference at least for media.

Because the fiscal year in Japan ends in March, and they need to sell something this year to have at least something in their annual report.

But I agree that a console launch in March would be weird and could be ineffective, it's a rather calm period and can be dead compared to the end of the year. And an underwhelming launch could be pretty bad for the rest of the console's life (example: Xbox One...).

You only base your analysis on precedents.

You shouldn't, Nintendo is actually trying to do things differently this time around.

They may reveal it in january for all we know and still releases it in march.

I'm not saying it's a good idea to wait. Just that anything can happen with Nintendo right now.

Because Nintendo said so.

Well they certainly can't wait holiday 2017. with Wii U and 3DS. Most likely they planned 2016. holiday launch, but from some reasons they needed to move launch, but they can't wait another whole year.

Obviously, since they said so.