USB to multiple RS485
A simpler option than four FT232Rs and a hub controller would be a single FT4232H.

The FT232H family supports a superset of the FT232R's features; it is frequently used as a JTAG controller. In this application, though, what matters is that the FT4232H can be configured to provide four UARTs. This allows you to do away with the hub controller entirely, along with all of its consequent added complexity.

And to combine some things further, you might be better off using a pair of MAX3030E and MAX3096 RS485 quad transmitters and receivers than using four MAX485s.