Atlus has a history of releasing second, enhanced versions of previous entries in the series, with both Persona 3 FES and Persona 4 Golden making tweaks to the original experience and adding in new content.
After rumours and teases over the last few days, Atlus has officially unveiled Persona 5 R. An announcement trailer has been released that reveals that more information about the game will be coming in March 2019. This video said that more information will be disclosed in March 2019 with the text "New Projects" appearing in the video, and also requested to visit the official website of Persona 5 R which is P5R.JP for more information.
Persona 5 R originally appeared among various website domain listings acquired by Atlus early past year, alongside PQ2.jp, which became the official website to Persona Q2 for 3DS.
Lastly, a new Persona News Channel post also has a little teaser, saying "A new message from the Phantom Thieves? Ultimate" in a DLC pack.
To gain credibility, the leaker outlined further details on top of the already-announced Joker DLC, suggesting that his appearance was tied with marketing for P5R - a complete version of Persona 5. This would explain why "New Projects" is plural.
That is all we know about the game at the moment.
Persona 5 was released in September of 2016 in Japan, and launched worldwide in April of 2017.