The most likely scenario is that there will be 2 SKUs for NX - or the handheld could in fact be the one without an optical disk-drive, i guess.
Still, spemanig, is right. Digital only devices are commonplace today... worldwide!
Although, one thing is downloading an Indie game (i know some are quite big) and another is downloading something like 30-50GB. This is where things may not go well and that's why i believe a SKU with optical disk-drive will and needs to happen.
Btw, remember all the fuss about having to download a firmware update when you started using your Wii U? It lasted more than an hour and people weren't exactly thrilled about it.
That's what can go wrong.
There are other ways to please retailers if a digital only SKU also gets released.
For example, they could have their own store on the eShop with special promotions (limited number of downloads, of course); download cards or special amiibo with codes at retail.
