Yeah... the T-team has been pretty chill about the whole leak thing. It doesn't really seem to have had any effect on the time frame, other than a bit of an afternoon put aside to disrupt someone's schedule. Nothing major.
As for Terraria being pirated in general, I'd be fairly confident in saying they're probably resigned to it -- Blue's responses re: Modding showed they're pretty aware that the game's going to get hacked into little pieces in due time. Whether that means they won't bother with more than token effort to implement DRM type stuff, I couldn't say.
As for pirating in general, it tends to boil down to a strict numbers game. Doesn't really matter how much any particular company or team puts into stopping it from happening, the internet just has more people and more time to spew at it than pretty much any other entity around. Anything and everything will be hacked and shared, sooner or later. Most DRM I've seen is more about making it "later" than not at all, to get the initial sales glut.
In any case, most of the folks I've seen admit to nabbing up the leaked version have also openly stated they're buying a copy as well -- some of them multiple copies. I don't think it's going to hurt Terraria much, if at all.
As for your dev dreams, White, better idea is to make something so awesome people will pay you for making it even after pirating it, rather than trying to stop them from pirating it
The former gets you money, the latter just wastes your time and goads the ones that do it as a challenge. The principle's more than a little off, there, but it's the reality of the digital age we're all, even if we don't realize it, really hoping comes about. It's better than the most likely alternative