I know this has already been stated, but Alice in Wonderland would be a great alternative new area to be added to the FL expansion. Not only that, but if instead of building all of these meet and greets, if they built a new attraction based on either version of the film (animated or Tim Burton's) that would have decent appeal for all audiences.
As for the rumored Frontierland expansion, I agree that it doesn't really make sense to expand Frontierland when other lands could use the help. Regardless, one point that people aren't really bringing up is that perhaps when they mean "expansion" they actually mean "re-purposing". Perhaps we will finally witness the end of Country Bear Jamboree and see it replaced with a new attraction with wider appeal (there have been old rumors about a Woody's Round Up ride). The whole thing of using TSI as an expansion plot would work, but would require a lot of work to happen and I'm not sure Disney is willing to spend enough money to do what that would entail.
Either way, I wasn't the biggest fan of the FL expansion when it was announced. I wanna go on Mermaid and eat at Be Our Guest, but other than that, since I am a college age male, none of it particularly interests me. In order to properly compete with Harry Potter, Disney needs to pull a giant rabbit out of their sleeve. I'm talking MI Coaster, DAK expansion, Imagination Redo/New Epcot E-ticket and possible other new MK attractions big. MAYBE something like all of that can take on Potter...