The problem with expanding Frontierland is getting people to the new expanded area... but over in Tokyo Disneyland they seem to have come up with a great plan for freeing up space
By moving Tokyo's "it's a small world" building, they not only add the pretty building facade that all the other parks have (...well? all the other parks except the world famous Magic Kingdom that is) but they can also use their big new show building to block the public's view of Space Mountain from inside their soon to be expanded Fantasyland, while at the same time freeing up space for some new Alice in Wonderland stuff where their "small world" currently sits
Now let's just say... "hypothetically" you applied the same logic to the world famous Magic Kingdom, and relocated the "small world" building to the same location it's going to be in Tokyo. You could then fill in the space between it and the Mad Tea Party with some new Alice in Wonderland stuff, and then all you would need to do is find a cheap way to re-theme Cosmic Ray's Starlight Cafe to some a little more "Fantasyland-esque" ...hmm, what could they possibly do with that big building... with transparent walls, and hexagonal rooms... hey! maybe something like this might work... "hypothetically"
So now we would have a great strategy for expanding not only Frontierland, but Fantasyland and Tomorrowland as well
now I know they only release the budgets in "One Year Increments" but they tend to plan this stuff out in "More Than One Year Increments" ...they painted the Yankee Trader "ghostly blue" almost a whole year before turning into a Haunted Mansion gift shop, they moved Tinker Bell out of The Adventureland over a year before they stared turning it back into a restaurant, and just last year they enclosed the outdoor section of Cosmic Ray's Starlight Cafe ...maybe they just felt they need more "nice, cold, air conditioned" space inside that already popular restaurant ...well the cold never bothered me anyway