1) Metroid games, unfortunately, as much as I would love this to be otherwise, have never sold incredibly well. Not poorly; pretty much every game in the series is a million units plus, but never on par with Mario/Zelda/Pokemon, and usually they aren't even on par with the middle tier of sales like Donkey Kong or Kirby. A Metroid game on the Wii U, a system struggling like it is, wouldn't somehow print money.
2) Wow Pokemon Snap really?
3) Nintendo systems haven't exactly been lacking in Mario, Sonic, or Mario + Sonic games recently. Trying to fuse them into one strange platforming mess (not even sure how that would work) wouldn't somehow make things take off.
4) This one's actually a feasible boost to console sales, but it would require a good bit of commitment on Nintendo's part to running servers and stuff, online being a realm that has never been Nintendo's forte. I have to wonder if Nintendo's worried about what releasing an MMO would do to future sales of Pokemon games as well. Might be not wanting to trade short term gain for long term loss rather than a simple hatred of money. I dunno.