I was originally scheduled for TPA-ATL-BUF on Monday Jan 10 but I have since changed it to TPA-DTW-BUF. When i changed my flights i was assigned a seat for the TPA-DTW flight, but for the DTW-BUF I wasn't assigned a seat and was told it would be assigned at the gate. I went online to try and get a seat but couldn't. Would I be safe to assume that this flight may be oversold?? The flight is 3719 from DTW-BUF.

THanks for any help.