In this case they showed the game running on the system just 1 week ago, it would be really weird if they do this now.

It's a vendor called Office Uk, it's not amazon, and it's an imported version coming from the US. The japanese version is not listed by amazon.

"この商品は、Office UK　　【アメリカから配送いたします。　※プライム商品は除く】 が販売、発送します。 この出品商品にはコンビニ・ATM・ネットバンキング・電子マネー払いが利用できます。

I highly doubt this is happening. While it would benefit the Switch in its launch year if it was only released on it, Nintendo knows the backlash from Wii U owners wouldn't be worth it, even if most of them are already buying a Switch anyway most likely. If this were to actually be true then that is just a downright dirty decision towards the Wii U owners that bought the Wii U for games like this Zelda.

They're previewed and demo'd the Wii U version plenty of times as well.

edit: To be clear, I would not be surprised in the slightest if this is something Nintendo were to do since they have made plenty of dumb decisions in the past, i'm just saying that I have high doubts about it though because surely Nintendo knows how much of a PR disaster this would be.

Like I said, PR catastrophe.

I'd argue the opposite. The PR backlash for this would be very, very bad. Like, very bad.

I actually think that this will be cancelled on Wii U. In Japan. This would push Switch sales there and that is their focus now. I still think that it will end up on Wii U in the rest of the world. But in Japan? I think its gone.

Nintendo is still very much catering to the japanese market. If anything I think Zelda would get a physical release in Japan and only digital everywhere else.

Obviously the PR backlash would be very bad, but I think sales wise it would more likely help the Switch rather than damper it, not by much though, but I imagine it would help, but it wouldn't be worth it. They would essentially be trading fan trust for a bit more sales. 

The demo (i've played it on Gamescom) ran surprisingly well. Yes, really.
And the game is still listed everywhere.
i think Zelda Breath of the Wild being the last Wii U game might be a save bet. It being cancelled is not.

I still don't think this is going to happen, it's a possibility... but I don't think so.