In 1.6, there will NOT be any weather changes, though they may fix the bug with pre-biome areas.
And if you don't think there would be a way to control biomes appropriately, then it makes WorldEdit that much more important, because if I can't fix the snow issue in my city, then I want to MOVE the city to a warmer biome, which I could do with WorldEdit.
SW-5120-1900-6153