I believe that it's a common myth that Qualcomm SoCs contain radios. When considering the RF that must be managed to deal with bus crosstalk within the SoC (system on (a) chip), adding raw antenna inputs and managing to that would drive costs through the roof.
According to Qualcomm, here's the modem set built-in to the S4 SoC -
From http://www.qualcomm....-new-mobile-age
Note, PDF download required.
Hope this isn't redundant and is somewhat helpful.
The Evo 3D submission to the FCC included a full schematic, with part numbers, that was fortunately leaked - I don't know if that's happened before or since, but was hoping for it with this phone (one can always hope). If we can get a leaked schematic, then as with the 3D, we can nail the entire phone's capabilities per various semiconductor data sheets and answer a lot of questions.
Sadly, as AJ suggests and you say, we'll most likely be stuck waiting for a teardown, and those aren't always complete.