Easy resolution: "disconfirmed" is the proper English word, and it should be used in any formal context. "Deconfirmed" is a colloquialism that is widely used in Smash discussions. As this is SmashGAF, I use the word that is most common within the community - when in Rome and all. Besides, "deconfirmed" just sounds better, and it fits better with "dehyped."
I think Palutena has a good chance. Kid Icarus got a jolt of life from Brawl, a new and rather popular installment came out for 3DS not long ago, and with all the new KI items, the franchise has more representation in Smash than ever. A second playable rep seems likely.
Shulk is a bit shakier. Xenoblade is a little more obscure (though no more obscure than KI was at Brawl's release, I suppose.) I can see Sakurai going either way on this: putting him on the roster like Pit, or relegating him to an AT like Isaac.