NX is basically nothing. It's just two letters to us. Nintendo is definitely making a new home console and a new handheld console. The only question is which one of these they will reveal in 2016, since they have confirmed that at least one will be shown next year.
I can't imagine them making it all the way to 2017 without revealing their next handheld. There's been a 3DS remodel almost every year of its life, and both New models released in 2014. Either they have another remodel planned (which would greatly surprise me), or the successor is imminent. For this reason I believe NX is a handheld. It doesn't make any sense to me for Nintendo not to announce a new handheld next year.
Iwata has already shot down speculation about their next home console and handheld being one device. Although they will be very closely related (perhaps functioning as a single "platform"), they will be two distinct consoles.
