You can actually get more than 65k connections per address depending on NAT technology. Traffic coming from 1.1.1.1:80 to 9.9.9.9:12121 can be mapped to 192.168.1.1:3333 while traffic coming from 2.2.2.2:80 to 9.9.9.9:12121 can be mapped to 192.168.1.100:9999. GCNAT devices usually support that.