Another data point, I was told today by Delta on FB that "Your ticket is not refundable nor transferable." when I asked if my ticket was changeable/refundable without fee since the original ticket was. That worries me slightly.
I was also told the same thing about not being able to change the outbound without repricing at current fare levels, so it's unlikely I would have been able to make the change anyways. I suppose I will just hold my breath and wait to see if DL cancels JFK-PRG over the summer....