Few may have noticed (or cared) but since the first set of trailers the trio's Keyblades have spontaneously changed their looks:
Terra's: Instead of 3 rows of teeth on the end, it now has two rows and lacks the curved blade on the tip.
Aqua's: Look changed entirely, more recent screens show the weapon's head looking all spikey and having no base under the teeth, while the original version looked somewhat like kingdom key/oblivion.
Ven's: Switched from left handed to right handed, and the teeth seem to have been flipped over (now resembling a normal Keyblade).
In addition: all 3 seem to have keychains at some point in the game (people HAVE noticed)
I think this is more than redesigning, the keyblades (in the presumed absence of form changing keychains) may actually evolve in some manner (I hope, Ven's 2nd design is ugly as sin compared to the first), possibly connected to the growth system, command board, or simply storywise
This would make the most sense with Terra, as design 2 shows his keyblade in a regressed form, which would be kinda pointless to keep as a permanent design.
Reason for Ven's main hand change is probably for camera angles matching other characters/consistent animation