Final Fantasy XV director Hajime Tabata just spoke out in a Japanese press release about the present success of, and planned future changes for, Final Fantasy XV. Some of those changes are going to affect a few late story beats, apparently for the better. There's a frustrating stretch of gameplay in chapter 13 that will be altered, and some added custscenes that will shed a light of clarity on some important events. The release is in Japanese, but the gist is this:
Tabata and his team are really pleased by all of the positive feedback from players. Final Fantasy XV has sold over five million copies worldwide, and Tabata wants to affirm his commitment to providing a complete and satisfying experience. To that end, he's provided a roadmap for free updates aimed at making the game richer, deeper, and more replayable. His goals were outlined accordingly:
"First, we will update the experience of Chapter 13’s gameplay. For that reason, we are undertaking many enhancements such as increasing the power of the ring’s magic. We will inform you of the details of updated content at a later time."
"Updating the production of the second half of the game, further enhancing the experience of the story. For example, we are planning to add event scenes where “What happened to Ravus?” was from. In addition to the event scenes, voice responses and localization work to all languages will occur so we will work firmly on this as a mid-term goal. Details of the plan will be announced once it’s decided."
"We will make it possible to use important characters that appeared in the main game as playable characters. We will also consider adding an avatar system to create original characters. In addition to this, we will continue to actively update so that various players can enjoy Final Fantasy XV for a long time."
Tabata also states that players will be able to start a kind of New Game + after completing the story, and a variety of new items should add to that experience and offer more replay value. Additionally, we can still look forward to the Gladiolus, Prompto, and Ignis story DLC, as well as some holiday and booster content.
I've heard some players express regret that they didn't wait for these updates before playing through to the end-game. If you want my advice, I'd suggest you just enjoy the game as planned; we have no solid release dates for any of these updates, even in the short-term. As soon as we learn more or get our hands on a North American press release, we'll update you with any new information.