If you currently use WebSphere Business Integration Interchange Server (WBI ICS) and you are looking for a migration path from IBM, you are in the same boat as many others.
IBM has WebSphere Process Server (WPS), but the tooling in WPS is completely different from what ICS is. WPS is the next version of the WBI-Server Foundation. However, the question still is, if I am an ICS customer, should I migrate to WPS? This is a constant dilemma for ICS customers. You could always have a detailed discussion with your IBM sales rep on the migration path.
However, if you have decided that WPS is the path for you, here is the link which talks about the process of migration from ICS to WPS.