Yes, you can expand with one NEB Port Expansion an get an additional RS-232 port, RS-485 port and timing options.
Or you can choose to connect other Impera Control Systems on LAN, e.g. Oscar, Sierra II, or in fact, all controllers with a LAN connection is a possibility.
Also, the switching relays, the PM4100, or AMP-D225H amplifiers have additional RS232 ports and GPIO's that can be used for expansion!