They will communicate just as the other clients communicate among each other, if the traffic is not passing through and triggering the NAT of the hotspot.
And it won't ...
Connect 2 devices in the Hotspot but do not login, if you try to ping each device you will notice that the ICMP will be successful...
The Traffic wont pass through the Firewall Facility ( L3 ) since the communication is on the L2...
Or lets say you have a network printer in a network where Hotspot is enabled, will you make the printer login to the hotspot ? No ... Do you need an IP Binding for the Printer in order to Print ? No...
You would need an IP Binding in case you want to access the Internet for Example without the need to Login in the Hotspot, or if the device in general needs to follow some routing paths ( reachable through VPN etc ... )