Some men aren't looking for anything logical. Some men just want to watch the world burn. While this may have been Joker's goal and mindset at one point, his first interaction with Batman must have altered that perception. While the desire for chaos to fuel his twisted laughter remains, Joker found a foil in Batman. Someone to share in the joke. Thus began a relationship that rarely shifts course: Joker instigates a crime for laughs or does something to cause pain for Batman, and Batman retaliates, beating him and sending him to Arkham behind bars, only for Joker to break out and continue the running gag. However, at some point, the punchline must come and the last laugh must be had, and Joker War just may be the final curtain.
While Joker seemed to be content with holding off the last laugh (to keep the fun going), recent events seem to have convinced him to make his move. Joker War is coming, which promises to feature Joker making a play for the punchline, going after Batman (and Bruce Wayne) in a final confrontation that only one of them may come out of alive. With Batman finding love with Catwoman, Joker seems to fear that the newfound happiness Batman carries may ruin his own relationship with Batman. He even went so far as to try and convince Selina Kyle to not marry Batman during their engagement, saying that Batman would cease to exist if he had happiness (which in part does prevent her from going through with the marriage initially). However, Batman and Catwoman are still together, and Joker can't be happy about it.
Furthermore, Superman has recently revealed his secret identity to the world, seeking to be his true self at all times. It's a game-changing move for Kal-El, but one that Batman probably won't imitate any time soon. However, Joker seems to be worried that Batman could reveal his secret identity all the same. Joker himself has known that Batman is Bruce Wayne for quite some time. However, he's done nothing with that information for the sake of keeping the running gag of their relationship going until now. Joker War promises that Joker will be fighting both Batman and Bruce Wayne equally, meaning that their next fight will be more personal than ever before.
It doesn't matter what version of Joker it is. It's clear he has never wanted to compromise his relationship with Batman. The Dark Knight Joker tells Batman that they're the unstoppable force and immovable object, destined to be together forever. The animated series version of Joker becomes disheartened when he hears that Batman might have died: "Without Batman, crime has no punchline." Even Lego Joker in The Lego Batman Movie is desperate to make Batman see their relationship in the way that he does, one that is special and more important than any other relationship either of them has. Most recently in the animated Harley Quinn series, Scarecrow unmasks Batman, revealing his identity as Bruce Wayne, thinking that that's what Joker would want him to do. Instead, Joker kills him for it, as he's now ruined an important part of their relationship: the mystery.
The point is this: Joker is going have the last laugh and end the running gag not just because he thinks it would be fun. He's doing it in part because he feels as though circumstances are forcing his hand. If he doesn't act now, something critical will change for Batman that might jeopardize Joker's chances for a punchline at all. Joker believes it to be the right time to enact his final performance, regardless of whether or not he's the one who lives at the end. Batman vs. Joker has always been one of the enduring rivalries of current pop culture. It's exciting to see that rivalry head into uncharted waters, even if it does end with one of their deaths (which it probably won't). These are two of the biggest comics characters of all-time after all.
Batman #93 starts the official "Joker War" on April 15th, 2020.