The only items worth keeping in prep for 2.2 are set items. The changes to them will be retroactive, but not completely. For instance the IK hammer won't get the new COTA damage buff it has in 2.2

Legendaries and new affixes on set items aren't retroactive. Only the sets bonuses themselves are retroactive changes. So you can save Focus and Restraint rings for instance, but saved Nat handxbow won't get RoV damage on it.