The idea of a fifth Lethal Weapon movie is something that keeps being brought up, largely existing as chatter from the cast and those who made the previous films, but never quite making it close to reality. According to Richard Donner, who oversaw all four previous entries, he's confirmed that he's still ready, willing and able to shoot the fifth.
Talking to The Telegraph (though much of the article is locked behind a paywall), Donner seemed positive about the idea, despite the hurdles such as the problematic position of Mel Gibson, the continuing global pandemic and the age of all involved, with Donner likely to be 91 when he shouts action. "This is the final one," Donner says. "It’s both my privilege and duty to put it to bed. It’s exciting, actually..."
Producer Dan Lin said last January that the progress on the new movie was closer than ever, and Donner's comments mark the latest statement from someone directly involved that it's still a going concern. Still, it remains a wait-and-see proposition at this point...