I see the next 2 weeks as nothing but downside for FWP.  If Mendenhall has 50 yards a game, everyone will say OK he played 2 tough defenses..we expected that.  If he happens to have a nice game or 2 vs these D's, then I believe the potential for full blow RBBC is there.  Only way the next 2 weeks can help FWP's value is if Mendenhall blows assignments left and right and fumbles in each game.
I personally see FWP as a sell (my league is very RB intensive though so I cant bring myself to pull the trigger).  His value thus far comes from the fact that he dominates the carries (ie there are no receptions to supplement the rushes), and I only see his workload decreasing going forward.  Plus what if he misses time even after the bye week due to the injury (that part is guesswork at best).
I was pleasantly surprised in Week 1 (we all were), but I see a lot of "17 carries for 75 yards with no catches" lines in his future.