Variety.com said Halcyon Co. heads Derek Anderson and Victor Kubicek are developing another sequel alongside the fourth movie's director McG.
Anderson and Kubicek have signed current Batman portrayer Christian Bale to play hero John Connor in three "Terminator" films, but they initially said they planned to wait until after the fourth flick comes out next summer to decide whether to make any others.
However, the entertainment industry trade newspaper said Anderson and Kubicek were so pleased with early reactions to the fourth movie they've decided to start planning for a fifth.
"We feel the time is now to start shaping the next part of this," Variety.com quoted Kubicek as saying.
Lytro unveils camera that can focus a photo after shooting it
'How to Train Your Dragon 2' releases 5-minute clip