I agree to an extent. The NX will have to stick with the same OS for as long as it's around, but it's not like it can't be updated later on.
3DS didn't even launch with an eShop. For all we know, NNIDs and friend codes could be abolished tomorrow, you'll update your systems, and we'll suddenly have cross-buy, cross friend lists, cloud saving, and all that. Don't need a new console for that.
There are a few things Nintendo has to 'get right', though:
Since game icons will have to stay a certain way from day 1, the NX home screen would mostly look the same. Sadly it's not something game companies are good at. The 3DS menu is the only one I'm satisfied with, and that wouldn't even scale to a tablet (or TV) that well.
I'd personally love a return of the Wii's channel layout. They're big, animated, bright, and detailed enough for a big screen, but still simple and neatly organised unlike the PS4 and Xbox One. I could work on a mockup if anyone's interested.
I'm talking about system-wide voice chat, listening to your own music while you play, stuff like that. As it would require a certain amount of overhead to be available at all times, the hardware has to be based around it from day 1. Please Nintendo