The first character in the Super Smash Bros. Ultimate Fighters Pass to be released is Joker from Persona 5, who was revealed at the 2018 Game Awards through an animated trailer. The only footage we have seen of Joker since then was a brief glimpse during the last Nintendo Direct which showed him from behind.
The world has been given a new glimpse of Joker thanks to an oversight on the official Best Buy website, which has revealed Joker's official render in Super Smash Bros. Ultimate on its Deals page.
The Deals section on the Best Buy website includes several pictures and links, one of which is for the Super Smash Bros. Ultimate Fighters Pass. The picture of Joker is his official render and it's our first true glimpse at how he will look in the game. Joker is shown wielding a knife but he doesn't seem to be carrying the gun that he can fire during battle in Persona 5, nor are any summoned Personas shown. This means that the render probably doesn't reveal much about his fighting style.
The fact that retailers have access to a picture of Joker suggests that he will be released soon. It was revealed during the last Nintendo Direct that Joker will be made available before the end of April, which means that he is going to be released within the next four weeks, assuming that he isn't delayed.
It's possible that Joker might be released on April 1 in order to coincide with April Fools' Day and tie into the theme of his name. However, it's more likely that he will be released on April 24, which is the date when more information about Persona 5: The Royal is due to be released. This will also likely be the date when Atlus confirms that The Royal is coming to the Nintendo Switch, as Nintendo isn't likely to put a PlayStation-exclusive character into Super Smash Bros. Ultimate.
Joker will be available as a DLC character in Super Smash Bros. Ultimate before the end of April.