If you use the same PSN ID, and have not logged into Destiny on the same PSN ID in any PS4 since August of last year, you will be prompted to perform the account import process that will provide access to your characters as they are on PS3 at the time of that process. If you have logged into Destiny on PS4 since last August, and therefore have already performed that process, your characters will be available as they were at the time of that import. Depending on when you purchased the expansion content for PS3, expansions I and II may transfer. The base game, and the Taken King, however, will not transfer at no cost. Destiny: The Collection, provides all expansions, including Rise of Iron.