This will be short.
"Soldier of Fortune: Pay Back is being published by Activision's Minneapolis office. We have no further information to share at this point, but hope to very soon", was all Activision revealed when asked about the next installment of the gory Soldier of Fortune franchise.
Soldier of Fortune is famous for its GHOUL system which allowed detailed decapitation and dismemberment (26 "gore zones" in SoF 1 and 36 in SoF 2 : double helix), but you already know that.
Don't take this seriously, but rumors have it that Pay Back is scheduled for November release. Expect to hear some real news during this year's E3.