Should I do this fantasy football trade?

Yes..you get two starting RB's for someone that is on the decline. Slation might have a few big games left this year, but you don't have any other starting RB1's on decent teams (although Forte is NOT a fantasy RB1 there's no guarantee that Pierre Thomas won't take carries away from Bush, and that KC will even score another TD this year- last week was a fluke).