It is logical, seeing as how the TX had a list of objectives.
Let's assume that it didn't though, what was it supposed to do after killing Sarah Conner? Self destruct? Go to Vegas? Become Governor of California?
I would think Skynet would have given it other objectives, to ensure it's future, and, if they are, indeed losing to the resistance, than the objectives might be to ensure their victory. Again, and though people complain about Terminator 3
, at least the T-X's programming made sense: Kill as many of John's resistance buddies as it could, kill John, and upload Skynet into our computers to bring about Judgment Day. While it failed partially on the first, and completely on the second, it did succeed totally on the third.