I think it will be closer to 100M than 50M with the potential to smash 100M.
-Nintendo still has something up their sleeve.
-I think the NES Mini will have a similar effect as Pokemon Go/Mario Run
-If the dock is just a fan and HDMI cable, then that's +$20 to have a console available in each room/friend's house/grandma's house
-Forcing/encouraging the use of local multiplayer on 3rd parties
-DS @ $150, Wii @ $200 (exc Wii Sports). $350 for NS sounds reasonable and doable.
-The DS acted as an advertisement for Wii software. Nintendo understands how important it is to get people to try their games. The NS is a walking advertisement and 'demo station' like the DS with the bonus that instead of taking turns, it's instant multiplayer which leads on to...
-Download play. You get to play the multiplayer part of a game you don't own (yet). There's no reason why you couldn't have access to a 'local' friend's game library while connected, no different than passing a cartridge over. Go one step further and allow people to trade, permanently or on a temp basis.
-I don't see siblings sharing the console for long. Like the DS, I think they'll demand one each. After a few price cuts, if the right software is there then Mum and Dad will want one too.
-It has the 'party' console thing going for it. It might collect dust most of the year but again, with the right software it will always be out at X-mas/birthdays.
-The potential of the 'fitness/exercise' genre is still untapped and ignored, the NS is the console most suited to tap into it.
edit -Game price. Possibly half in some cases of what a new release costs elsewhere.
The NS reveal and reception doesn't seem or feel anything like the 'wow' reaction the Wii got.
It has a similar 'hmmm?' reaction/feel as the DS.
How does a system with the third party support of the DS alongside doubled first party output not beat 3DS at a minimum?
Don't Play Stationary 4 ever. Switch!