Well, as it is they *are* winning, from what we've been presented. The real question comes down to, was it worth the cost, and will they get all the goodie infrastructure they wanted out of the deal. Otherwise they semi-avert a civil war. They can take Earth, it just comes down to how many ships they commit, and how many holes they'd have to blow in the crust to get the Sol government to cave. There is a point that they would, it's just a question of when and how much lives they are willing to sacrifice. They could have the whole pie if they were willing to wait, but they aren't.
Personally, as a supporter of the other side, I'm kinda curious how the Pro-GTVA side seems to be the default on the forum - at least from what I've read. Is part of that nostalgia from the original games? I admit, I just can't stand the 'command talking head' guy, so maybe that's coloring things a bit.
Strike that first part - just realized that act 3 had been released. I guess I should get around to playing that before commenting.