You may look at the above picture and wonder, "Why would Skynet send a toddler back through time?" Well, this photo was part of an early concept for another film in the Terminator franchise. The idea was that Skynet would send a toddler back to the mid-1980's to assassinate John Connor at his daycare. The idea was shot down for several insurmountable complications: (1) The writers couldn't figure out a sensible way to get John Connor into daycare since his mom was on the run with him in Mexico when he was a toddler. (2) The studio couldn't figure out how to advertise the movie--was it a sequel or a prequel? It's a sequel to the first movie but would be a prequel to Terminator 2. Could they call it a "midquel?" The curse of time travel falls heavily here.
Now they've thought of a way to morph the idea to please the fans. Since a good deal of the blame for the terrible atrocity that is Terminator: Salvation has been pinned on director McG, a brilliant idea was brought forward. The producers could make it up to the fans of Terminator with this plot line: What if Skynet sent a toddler terminator to kill McG in daycare, thus wiping out the possibility of the great disappointment of the fourth movie? Revenge fantasy seems to be all the rage (see Quentin Tarantino's Inglourious So-And-Sos, or, better yet, don't). Also it would introduce some moral complexity: who do the fans root for? Normally they'd root against Skynet, but hey, it's a whole new situation here. Filming two alternate endings (one with Skynet winning, one with McG winning) could keep the ambiguity going and would make a great feature for the DVD release. Maybe they could gimmick up the theatrical release and have two different versions of the film showing. The fans could vote with their ticket stubs on which is the one they really want to see.
Maybe it could happen--there is no fate but what we make.