Wait.
Scenario 1:
* GS3 drops in price, new GNex out and rocks your socks off.
Dilemma: save money over getting the GS3 or pay more for the GNex (though it may actually have a lower introductory price)
Scenario 2:
* GS3 drops in price, new GNex out and it sucks
No dilemma: Get the GS3, save money, profit
Scenario 3:
* HTC and/or Moto introduce new superphone over the next 2 weeks, you buy GS3 now.
Problem; you have GS3 but HTC or Moto phone won't be available for purchase til just outside the 30 day return mark. You curse the world and everything in it.
Scenario 4:
.... you get my point.
Yes waiting in tech world is kind of a silly concept but you're also coming up to the time of year when great deals are likely to come around and the next GNex and/or HTC/Moto/Sony/whatever (sorry LG) come out with the next superphone, or heck you might want the GNote2.