Wii U's disc drive draws something like 2w-5w max (we did the math in the old GPU thread. Things got pretty heated. haha). It's really not that big a factor in power draw. In fact, having that optical drive in there probably helped them with heat dissipation, as a fatter box allows for more airflow and larger fans than an ultraslim device. Gamecube is probably the nicest example. Xbox One vs. PS4 is the latest display for core gamers, as many complain about the PS4's jet engine fans. They need to spin fast because of how slim Sony designed the case.
I'm still conflicted as to what type of storage solution I expect Nintendo to take. They could very well stick a Gamecard slot on the NX console (or controller), but 64 GB cartridges still seem to belong in the realm of fantasy. Some of you may want to read some of the posts in
this Beyond3D thread on the topic. Digital downloads are what Nintendo want to move towards and possibly in combination with a small capacity Gamecard or NFC "key" for authentication. For games requiring a large amount of storage, besides digital, optical media is still the cheapest way to go. It's best for the consumer, publisher, and retailer. Nintendo will figure out a way to pull off crossplay (if that's truly what they want for most games) that does not require a 64 GB "cart".