So I just saw the Galaxy S6 on the Boost Mobile site. Says its coming April 2015.
http://www.boostmobile.com/shop/phones/samsung-galaxy-s6/?icamp=INTC_HP_Panel_Row2Col2_GS6PreReg
http://www.boostmobile.com/shop/phones/samsung-galaxy-s6/?icamp=INTC_HP_Panel_Row2Col2_GS6PreReg