CAA is currently shopping a rights package to various different studios with both Arnold Schwarzenegger and Justin Lin attached. Robert W. Cort is producing, though no screenwriter has been hired at this time.
Pacificor currently holds the rights to The Terminator franchise. Universal, Sony, and Lionsgate are all reportedly considering the package that CAA has put together.
Like Man of Steel, which sees Warner Bros. in danger of losing certain rights to Superman, there is a rush to get a new Terminator into production soon, as the rights will revert back to James Cameron in 2018. Though he has no plans to ever make another Terminator, he would have to be included in any deal that would see another film go into production past 2018.
Currently, there is enough time to make two new Terminator movies before that has to happen. It is unclear at this time if the next chapter will be Terminator 5 with Arnold Schwarzenegger reprising his role as the unstoppable killing machine, or if it will be a new take that finds the ex-Governor playing a new, different role.
More on this will be released in the near future.