This probably won't come as a shock to you, but the major U.S. carriers will carry the new Galaxy S4 flagship from Samsung. US Cellular, Verizon Wireless, T-Mobile, Sprint and AT&T have each issued statements confirming this. Of course, it would probably be very surprising if any of them chose NOT to carry the hottest new device on the planet. Of course, despite announcing their support of the new product, none of them have given out any pricing or dates for the device, but a couple of them have information sign-up pages.
We don't have any of these sign-up pages from Sprint or Verizon yet, but here's a couple below from AT&T and T-Mobile. Please add links to other sign-up pages to this thread if you see them. Thanks!
Early Info Sign-up Websites for Samsung Galaxy S4: