Yes, the two different WAAE agents can co-exist on 1 host.
The items to be aware of are to not mix the directory structures or ports.
Please make note of the operating system type/version to make sure what is being attempted is supported.
WAAE 4.x was dropped from support as of 03/15/2013 and was never certified on many of the newer operating systems.
While the newer WAAE 11.3 agents do not support many of the older operating systems.
Here are the CA Workload Automation Release and Support Lifecycle Dates:
Here is the current 11.3 system agent matrix: