Looking at that picture carefully, I'm not convinced the MGM sign won't be coming back. As I said above, the arch has been under an extensive rehab over the past month and a half complete with new tiles and painting scheme. If they were not planning on putting up a similar sign, the brakets/holes would have been re-done at this time, no question.
However, looking carefully at that pic in this thread, it matches the placement of the old sign almost perfectly. There is definetely the holes for the STUDIOS letters and the brackets/holes form a pattern that would hold the old Disney-MGM title line and the Lion logo above it. Its still premature to say MGM is no more even though the contract with them has supposedly ended. But who knows, a new sign referencing WDSF may have been made to fit right into the old signs brackets.