Apart from getting ready to introduce the SPH-L710 (which is probably a Galaxy S III version), Sprint is also planning the release of the Samsung SPH-L300. Like the L710, the L300 will have LTE connectivity. Moreover, it's said that the L300 uses the same dual-core Snapdragon S4 processor. Brief Mobile has a photo of the Samsung SPH-L300, showing it to sport three physical keys.
Unwired View, Sprint's new Samsung SPH-L300 LTE Android phone pictured