Rush Hour 4

Jackie Chan has admitted that he was not interested in reprising his role as Lee. He says that he would only reprise his role if the script is good. Chris Tucker on the other hand, joined in not even looking at the script

Shortly after the release of the third film, Brett Ratner had stated that he would not return for the fourth film as a director. Although, in the spring of 2017, he had expressed interest in returning, even jokingly calling it "Grumpy Old Rush Hour" (a play off the film, Grumpy Old Men (1993)) and asking Shah Rukh Khan to appear with Chris Tucker and Jackie Chan in the proposed India-based sequel, it is highly unlikely that he will be involved with any further sequels given his numerous sexual assault allegations that surfaced in later that year, including a claim from actress Sarah Shahi who stated that on multiple occasions during filming of Rush Hour 3 (2007), Ratner pushed his groin against her and made graphic sexual comments.

It still seems more a matter of when than if Lee and Carter reunite on the big screen, but the project remains speculative, so details are scarce.