As seen before, Rockstar allowed to port PS3 GTA V character to the PS4 version of the game for a limited time. Do you think that Rockstar will allow to port your GTA V character to GTA VI? Personally, I don't think that they will allow it. It's an entirely new video game and there are a lot of reasons for not allowing it. Also, there are a lot of modded accounts and if they allow porting they would probably lose money as they expect people to buy a lot of Shark Cards in the beginning but with the modded accounts that can't happen.