The FLE is a perfect example of TDO's thinking. It was NOT designed to increase attendance. It was simply to replace the capacity of lost attractions such as 20K Leagues. Even though it was announced in 2009 (a full 2 years after Potter was announced) TDO felt that Potter was actually going to only help WDW. As it turned out, that was not the case. In fact, Potter hurt WDW's numbers slightly, but Potter sucked the life out of in park guest spending at the Disney Parks. The One Disney/Disney Parks generic merchandise only compounded the situation.
I believe that had Potter opened before the FLE was planned, I think the FLE would have been a titch more ambitious.