T4 being PG-13 is not the end of the world.

So what Terminator 4 is rated PG-13, it isn't the end of the world. As long as the story is coherent with the rest of the series, as long as the special effects and action are top notch, and to top it off if Christian Bale can pull off the role of a bad ass, war hardened John Connor in the post apocalyptic future then we have nothing to worry about. The movie can still be badass without the need to say "fuck" every five lines, and without an insane amount of blood and gore.

Now just to point out this is a clever ploy on behalf of the producers of the movie. When a movie is rated R a certain percentage of movie goers will not be able to see it, which means less money. Now when it is made PG-13 more people will be able to enjoy it, which means more money. Plus also when it becomes DVD time the Unrated version will sell like hot cakes if it promises a lot of stuff that was cut from the movie, or altered to achieve it's goal of PG-13 status.