Well they have to wait for a movie deal to fall apart first. A Magnum reboot was initially going the path of Starsky and Hutch or 22 Jump StreetI think the networks must have a list of every old tv show and they just run down the list, checking them off as they decide to make it the next reboot, yet somehow they never get to ones you want to see like Quantum Leap,Northern Exposure or Wonder Years.
Jason