I believe that Nook will be playable, as not only is it easy to remove him from the background, but he's also wearing one of his lesser known costumes, which always struck me as odd.
That being said, he shouldn't be removed, as its a double standard. Thus, even though I think he'll be in for sure, I adimit there is a lack of evidence, and that he should stay until further notice.
The only character I completely disagree with there is Lip, as that's just a dumb reason to deconfirm, as shown by things like the screw attack, fire flower, pokeball, and others. >_>