DLC packs
A lot of My Fairy stuff, and adventure maps; likely no new battle maps which is a shame.
Pack 1 is held up by the free Medli and being early; still an adventure map can't go amiss.
Pack 2 is Link's Awakening with a character and Linkle Weapon... The only characters that come to mind from Awakening is Marin and the Owl. Both are reasonable as they were the origins of recuring characters Malon and Kaepora Gaebora. If I were to guess I'd say Marin using the Owl as a weapon possibly with a Malon alt and Kaebora as the lvl 3 weapon. As for Linkle's weapon... Okay, maybe that's Owl... Roc's Feather made it's first appearance in Awakening, and Magic Powder and the Shovel are both unused but I struggle to think of anything. The Wind Fish could also be a thing, though how exactly that'd work I have no idea.
Pack 3 combines Spirit Tracks and Phantom Hourglass for a character and Toon Link weapon. Given the combination I feel 1 from each is the best bet. For characters Linebeck seems the most popular (with his spyglass as his weapon?) and he is a legendary captain, but they could of course leave it to Alfonzo... As for weapons there's always the titular Hourglass from the first game (how that would work I don't know) but the second has more potential in my eyes with the train and phantom zelda both being solid options.
Pack 4 ditches the character weapons for 2 playable characters from a Link Between Worlds. I feel this is one of the easiest to guess as Yuuga and Ravio stand out by a mile. Hilda is also a posibility I guess, but I feel fairly confident in Yuga Ravio combo.
Of course these guesses all rely on one thing mind you, that the characters and weapons are actually related to the packs adventure mode, and that may not necessarily be the case. It is nice to see the handheld games getting recognition, but it is sad that Minish Cap (Vaati playable, 4-sword Toon Link) and the Oracles games (to be fair with all 3 oracles and animal buddies as options I can see why) appear to have been skipped. Hopefully Hyrule Warriors NXtreme Legends doesn't disappoint.