The answer is yes. The ControlLogix Gateway is transparent to the protocol.
The PLC5's and SLC5/05's use the original PCCC (Programmable Controller, Communication and Command) protocol to enable all comms.
The newer ControlLogix (CLX) processor's primarily use CIP (Control and Information Protocol) to exchange data, although they are also capable of supporting the old PCCC messages as well.
BUT here is the key...the Gateway configuration you have does NOT pass messages through a CLX processor, so it's presence or otherwise is not an issue. In fact one is not even needed to make the system work.
Your data will move directly accross the backplane via the 1756-ENBT and 1756-DHRIO modules which support both CIP and PCCC. This means that your old Interchange application will work, without any changes.
The old datatable addresses will work just fine, and the 1756-DHRIO module will need to be configured (using the Gateway Config software) to map the old DH+ addresses to the new Ethernet ones. This is a simple task.
Overall it should be pretty easy to get going.