Richard Donner on Lethal Weapon 5! 2014 interview
This is only from two years back, and Richard states that he wants to do the movie, that Danny is ready to go, that Mel is ready to go, and that he hopes it gets made.
https://www.youtube.com/watch?v=yav53dtSFyA&feature=youtu.be
Go to 16:23 to hear this part!
I wonder what Shane Black thinks about this, as I know he's mentioned the movie not happening.
Hopefully when the horrible looking series bombs, the studio will do one final movie with the originals back, if Mel agrees.