It seems that every character who has returned from older games have kept an ability that represented them so well, but seem to have been their more strategic moves. Here is what I mean with the following:
Life:

lost her daggers and possibly her speed move, but can still go into stealth mode.
Earth:

doesn't just punch anymore and now shoots little sharks instead of summoning them, however can still dig underground.
Air:

had the biggest change as he no longer can soar and can now shoot enemies he sucks up with his new weapon.
Water:

no longer uses harpoons or his hose, but kept his water jet pack.
as for the others, here's what I think will be the moves kept for each of the other elements.
Undead:

will most likely lose her claws and the shooting blades, but can still roll and headbutt enemies.
Magic:

obviously no longer throws bottles since he now has a tuba and will still have his beast mode to compensate.
Fire:

will most likely lose his lava lobs and maybe his magma balls, while keeping his eruption attack.
Tech:

is a tricky one to determine. Perhaps still obviously shoot coins, but no longer can lob gold on enemies or use his Yamato blaster.
These are my thoughts on what will remain on these characters. Please give me your input on your thoughts on this matter.