Here's why it will suck:
1. First & foremost: Arnold is a has been. He vowed that T2 was the last one when it first came out in '92, yet now he is back in the saddle. I doubt he was persuaded by the money, as he doesn't need it, moreso by the fact that the guy hasn't had a decent movie in years. He is out of touch with his audience. Personally, I admire the man for all he has accomplished. I'll never accomplish a 1/10th of what he has in my lifetime, but that isn't going to make me believe that he can bust through walls, or smash through a ceiling and into the floor above him, even though his character is mortal(not a Terminator). His acting is tired, and the one liners were stale 10 years ago.
2. James Cameron isn't on board. Why? Because he though the storyline was lame and wanted no parts of it. I also believe that he is sticking to the "T2 was the final installment" angle as well, as was stated in '92. Then again, he had "Titanic" since then, or he might feel differently. I equate his views on not wanting any part of T3, to Jodie Foster not wanting anything to do with "Hannibal". She though it was weak, and it was. Don't underestimate the loss of Cameron here. He jumped ship after Alien 2(aliens), and you see where that series went. 3 sucked, and 4 was so/so at best.
3. I heard, but am not sure, that the third installment is going to be rated(or they are pushing for it to be rated) PG-13. If that's the case, you can bet your bottom dollar that the "edge" will be long gone. That stroyline is all about violence(the end of the world, and Nuclear War usually is), and to try to dumb it down for the sake of being PC, or attracting a bubblegum audience is going to hurt the storyline BIGTIME. Still, I'll go see it I'm sure.
All that said, I thought the trailer looked really good. I really like the idea of the Woman Terminator. Warik, I think the plot will be that potential "targets", are less likely to suspect the woman being the terminator, and thus the reason why the T-X was designed as such. Just a guess.