Now, that Travis Brown is only out 4-6 weeks (good news) and Losman will be back by season's end, the Bills will be forced to cut the veteran they sign when Brown is healthy enough to play. You cannot keep 4 QB's on your roster for long. This may make signing that veteran QB (O'Donnell, D. Johnson, Kordell, Mathews, etc.) more difficult without sending Brown or Losman to IR.
As insurance, they will cut Zolman (when the veteran is signed) and sign him to the practice squad.