In 1.5, new keyblades were added to game. Now in 2.5 I believe that new Keyblades will also be added to, probably, both 2 Final Mix & BBS Final Mix and maybe some Keyblades from the other games.

BBS FM: I think there will be new Keyblades for completing the Command Board, completing every story/defeating each final boss for each story, defeating Aqua's Terra-nort, finishing the final episode, and finishing the Mirage Arena.

KH2 FM: New Keyblades for 2 FM would be Finishing BBS FM first, beating the Lingering Will, beating all the Data Org. XIII, and beating the Absent Silhouettes.

For returning keyblades, I'm not really sure because there are a lot of them that I want to come back.

Actually the only new keyblades that appeared in 1.5 were Diamond Dust and One Winged Angel that already appeared in the orginal final mix version so the new kh 2 keyblades will be two become one and winner's proof.For bbs fm we'll get crown unlimit by defeating no heart which was also available only in the final mix version of the game.

No new keyblades were added in KH1.5; the KHFM keyblades were already in the original Final Mix, and the added keyblades in Re:CoM were just cards with images of the keyblades painted on them, and had some unique effect. Square probably isn't going to go through all of the trouble of adding new keyblade models to the games - neither BBSFM or KH2FM. I wouldn't completely deny it though, since anything is possible. 

Like previous members said,there are no new Keyblades will be appeared in 2.5 since some of the Keyblades has already appeared in the original Final Mix...

Can't wait to get my hands on Winner's Proof.

Can't wait to get my hands on Winner's Proof.

Well,to get that,you have to complete Org.XIII's mushrooms challenge,but good luck with that!

Actually the only new keyblades that appeared in 1.5 were Diamond Dust and One Winged Angel that already appeared in the orginal final mix version so the new kh 2 keyblades will be two become one and winner's proof.For bbs fm we'll get crown unlimit by defeating no heart which was also available only in the final mix version of the game.

Seriously, does no know know what this HD collection is all about? I've seen several people posting here seemingly completely ignorant that there even ARE Final Mixes. 

That could happen. And if it does then Happy Playing!