Kingdom Hearts 3 director Tetsuya Nomura revealed that DLC for the game is currently in development. This applies to both free and paid DLC updates. Nomura also said that free DLC will likely be released through small updates as soon as they are completed. Paid DLC will feature larger updates, and could be released within the year. There is no specific date as to when the DLCs will actually be released.
This information was revealed through an interview with Dengeki Online.
It should be noted that last year, Nomura revealed that instead of selling in-game items, the development preferred to have gameplay expanded through content updates. If there was to be any DLC post-launch, it would not be limited to cosmetic items. Nomura also said that if they would go the DLC route, it will not be through a Season Pass but instead a standalone.
According to Nomura, the paid DLC is expected to fill in some gaps present in the story. There are already a number of story gaps in the game and the release of the secret movie, as well as the epilogue, just made things even more difficult.
In the same interview, Nomura said that the development team will add Critical Mode to the game within the next few months. The team is currently making adjustment to ensure that the Critical Mode offers a unique experience rather than simply increasing the difficulty. Players of the Kingdom Hearts series should be familiar with Critical Mode, as it limits players' abilities and health.
Nomura also revealed that in the past, the Critical Mode was generally added in re-releases of games dubbed "Final Mixes". For Kingdom Hearts 3, the content will be released on a piecemeal basis.
While this is certainly good news for fans, it should be noted that all of these information is from Nomura himself. There is still no confirmation from Square Enix on how the game will move forward. However, the fact remains that Nomura and his team are indeed working on DLC and that is something that fans of the game can look forward to.