I2C only has 127 addresses and some of those are reserved for other purposes and really aren't available.
The limitation of I2C comes from bus capacitance. That includes also the capacitance each device on the bus adds. Even with a bus extender you have to find a balance between overall bus length and number of devices 100+ devices AND 300 ft of bus lengt is rather unrealistic aside from falling sort for the number of devices you want to connect.
I am not aware of any low cost bus system that can accommodate 512 devices.