Arnie always promised that he'll be back, and it looks like Terminator 5 now has some writers attached to it. Laeta Kalogridis and Patrick Lussier have collaborated on previous movies before, with Lussier known for the Nicholas Cage movie Drive Angry, while Kalogridis' credits include Shutter Island and Avatar.
Fast Five director Justin Lin was previous attached to T5 as the director, but has moved on due to scheduling issues - mainly because the Fast and the Furious franchise is still making loads of cash - and now we have David Ellison getting into the director's chair.
Ellison has gotten involved because his sister, Megan Ellison, paid a large sum for the Terminator rights through her company Annapurna Pictures. David Ellison is known for his work through Skydance Productions, who have worked on Mission: Impossible - Ghost Prototol and the upcoming Star Trek Into Darkness.
Hopefully this means Terminator 5 gets thrown into production in the coming months or years, and now that Arnold isn't the Governator anymore, he's free and doing movies. I'd love to see a cameo with him, and not some CG junk from Terminator Salvation.