I'm not sure if Rockstar will ever fix this, I think it would take away some of the things in the game that are important. When you think about reducing frame drops, they would most likely have to take some things out of the game, because the game is putting your PS4 underload when trying to load all the graphics, motion capture, details, objects and other things all at once, which is why it does the frame drop when entering towns.
I honestly think this is a problem, but I wouldn't consider it to be "unplayable" and I also don't think it should be a make it or break it for the game.