Except Super Mario Maker sold about 3M copies, AC: HHD sold about 3M too, FE: Fates sold 300k in 3 days in US, Splatoon sold 4M copies... Nobody knows about them I reckon. 

I can't say this comes as a huge surprise. Nintendo are making a lot of changes and that costs money, similarly there's nothing huge on the immediate horizon that could turn things round. So, yeah. Not good but not a surprise.

Another reason why the NX is likely coming in 2016. If it's ready, it will arrive in 2016.

There are 2 key points as to why both revenue and profit guidance has been revised down.

1. Exchange Rate for Japanese Yen
2. Lower than expected 3DS Hardware and Software sales

The R&D costs were always factored in to the guidance and they won't have suddenly increased spending this year for no reason.

What is of note though is that they expect Wii U software sell in to be slightly higher, I imagine this is due to the continued success of Splatoon & Super Mario Maker as well as the release of Nintendo Selects titles.

What you're failing to mention is that this is a revised forecast from Nintendo themselves. They were actually expecting to do better this year but ultimately have had to revise their forecast down due to the reasons above. 

With all that said, does it make the NX the most important/crucial launch ever for Nintendo?...Since the NES, have the stakes ever been so high?

If the NX fails to take off then we could have a Blackberry situation on our hands where revenues from traditional segments decline sharply whilst new segments are unable to offset the decline at all. 

The WiiU isn't selling, the 3DS sales are going down, they have less and less software to sell on the WiiU, and they are currently spending a lot of money to prepare the next gen.

All that and they finish the year without any loss. I'd say that's a big win for one of the worst year the company has ever known. Thank you Amiibos and strong frist party sales.

I'm sure they were way more nervious with the launch of the Wii/DS and their huge potential of failure, but at least at that time they still had the monster that was the GBA. But yeah, they need to improve their hardware sales. If Nintendo unifies their platforms and keeps those wonderful attach rates, a 60-80m userbase on the NX, both handheld and HC, would be enough to give Nintendo the stability they need.

Rather than just yelling doom, or that there aren't enough Wii Us being sold, it might be beneficial to actually look at what was modified in the modified forecast.

Wii U hardware sales are still forecasted at exactly the same as they were before, and the Wii U Software is forecasted to be 40 million higher than in the previous forecast. Clearly, a lack of games on the Wii U is not the reason for the lowered forecast.

The 3DS is modified somewhat downwards, with both software and hardware sales being roughly 1/6th lower than previously forecast.

I'd also like to point out that the OP's claim that the revenue is slashed by half is incorrect. Net sales - which is more or less revenue -  is 15% down from the previous forecast, and 10% down from last year.

Their forecast operating income is down from the previously forecast operating income, but up from last year's.

The only thing that's taken a huge plunge is the ordinary income, and that's happened largely because of the exchange rate. There's no "Trying to blame it on exchange rates when it's really that they're just not releasing games this year", because the reason for the large drop in ordinary income isn't lower revenues. 

ZhugeEx has this completely correct.

Eh, what ever. NX, baby.