The new film will be contingent on the success of latest instalment Terminator: Salvation, which is released this month.
"I strongly suspect the next movie is going to take place in a [pre-Judgment Day] 2011," he told Film Journal.
"John Connor is going to travel back in time and he's going to have to galvanise the militaries of the world for an impending Skynet invasion. They've figured out time travel to the degree where they can send more than one naked entity."
The filmmaker also said that the futuristic machines known in the film series as hunter killers, transports and harvesters will do battle with modern-day military war machines.
McG added that he would feature former T-1000 Robert Patrick in the fifth film as a scientist doing stem-cell research.
Terminator: Salvation is released in the US on May 21 and the UK on June 5.