I believe they are positioning it as a replacement for mainframe batch workloads written in JCL, along with rewriting the associated COBOL code in Java. Run WebSphere for z/OS on the same machine as your existing JCL/COBOL batch workload and then slowly rewrite the COBOL into Java and the JCL into JSR-352 JSL, and IBM has Java APIs for VSAM/IMS/etc so you can still access your existing mainframe data from the new Java code. Even if XML is no longer the hotness it was in the early 2000s it is still an improvement on JCL, and it is easier to rewrite batch-oriented COBOL into batch-oriented Java than to change its batch-oriented nature into something more real time.