If you already have a year 1 exotic armor piece you will always have access to that year 1 armor piece at its year 1 base level. If you decide to dismantle that armor piece or it gets lost you can purchase it again with its signature perk unlocked. At that point you will need to level it back up to the maximum level with experience. If that particular piece has been brought forward then you can keep the year 1 you've already leveled and buy a new year 2 version with no perks unlocked. It will come at year 2 max level and experience will unlock the perks. Same goes for weapons with the exception of the signature perks. These are not intrinsic for either year 1 or year 2 versions. The year 2 version will come at a set year 2 damage level and be able to be infused with other weapons to keep it current. The year 1 version will be just as if you found a new one in the wild.