Yeah, this is why I voted "no" on expansion, because while I believe it'll lead to new experiences, I highly doubt much will be taken out of new land acquired by the property. Any new attractions will be at first replacements of old ones. Potter will, however, make them take pause. The amount of influx they will get for at least a year will be far too strong to warrant any closures/construction.
Universal will most likely skyrocket to meet Disney's numbers, if just a couple dollars less to make it seem like the consumer is getting their bang for their buck.