Last we heard on Terminator 5 was that Arnold Schwarzenegger was taking a break from pursuing new film roles in order to manage the love-child scandal. The news came just as Arnold had announced a number of upcoming film projects, most notably as part of a package that would see him returning in some capacity for the next Terminator sequel. Indie savior (and billionaire producer) Megan Ellison won the rights to make the next Terminator movie, and apparently is doing so with both Justin Lin (Fast Five) directing and Arnold Schwarzenegger starring. However, the Schwarzenegger scandal brought all updates to a stop. Now, What's Playing has a few extra rumor nuggets that suggest the sequel is still very much moving forward, with or without Arnold's immediate participation.
Considering the fact that they need a script and cast, there's plenty of work to do that doesn't involve Arnold at this point in time. That, plus the fact that many major Hollywood scandals usually play themselves out within a few months, means our former Governator should be ready when they're ready for him. WP claims the sequel will reboot the franchise in the same way that J.J. Abrams did for Star Trek (and what Fox just did for X-Men) -- by bringing back the same characters from the original movies, only having them be played by different (read: younger) people. For example, Paul Walker's name has been rumored for Kyle Reese, a role originally played by Michael Biehn (and then again played by Anton Yelchin in Terminator: Salvation). The casting choice makes sense, especially since Walker has worked a lot with Lin in the Fast and Furious movies.
So what about those earlier rumors about the original cast returning? Well, as we saw in the recent Star Trek (with the cameo by Leonard Nimoy), that could still be the case. It all depends on how they play with the timeline, and whether the story calls for an older version of, say, Kyle Reese, allowing Biehn to reprise the role. Either way it seems like they'll be pulling a Star Trek by creating a new timeline that allows them to reuse the same characters, but in a different story -- perhaps one that connects the old timeline to the new one so that they can play with the original castmembers too, like Arnold Schwarzenegger.