The currents that hold the 2GP in place have their counterpart in the South Pacific - the South Pacific Gyre. That's where plastic bags and other trash from the East Coast of Australia and New Zealand would end up if they actually made it into the open ocean without snagging on a coral reef, the west coast of New Zealand or some other obstacle. Perhaps there's a Lesser Pacific Garbage Patch out there, waiting to be discovered.
And when it is discovered, we'll show those Canucks, Yanks, Japs and Chinks a thing or two, when the unrestrained growth of our Pacific Garbage Patch outstrips the growth of theirs and they have to cede the title of Great Pacific Garbage Patch to our oceanic soup of plastic. Because that's what being Australian is all about - boring it up anyone who isn't Australian, any bloody way we can.