Merrick here...

A password protected industry tracking site called trackingb.com says that Shane Black is at work on a fifth LETHAL WEAPON project. It's currently unclear whether he's developed a full spec script, or has only handed in a treatment.

We are now hearing that Shane Black may have only handed in a detailed treatment to Joel Silver and that they are taking two old scripts and mashing them together to make LETHAL WEAPON 5… Also hearing that Silver is after Columbus Short for a role

...says the article, which you can find HERE.

Trackingb says Gibson and Glover are interested in reprising their roles. No other details are given, except that 1) franchise producer Joel Silver has already been contacted by Black, and 2) the storyline would deal with an about-to-retire Riggs coaxing an already retired Murtaugh out for a "ride off into the sunset" case/adventure.

I love what the LETHAL WEAPON films reprensent in terms of energy and attitude, although I found myself quite tired of the whole shebang by the time #4 rolled around. If this project fleshes out, Silver. & Co. would presumably go after Donner to direct. Let's hope Joel and Dick put the screws to the studio (Warners, I guess) and don't settle for a diluted PG-13 rating. The others were hard 'R'...respect that & leave it there. It's tough enough to imagine more of this shtick, but having the same shtick watered down?

It should be noted that LETHAL 5 rumors have been in the wind for a while now - most visibly in the slipstream of Gibson's...incident...when it was claimed Mel wanted LETHAL 5 as a way to regain his footing.