I work for a large brokerage company that has a deeply integrated system written entirely in COBOL on the IBM mainframe. That sucker is going no where, and for good reason: it's incredibly efficient for what it does. As a batch processing system, the mainframe simply can't be beat. We deal with millions of dollars worth of transactions every day that have to be correctly accounted for and reconciled. In order to get the performance required to do all of that, we stick to the mainframe.

However, I do see the appeal for building off of the COBOL foundation using more modern languages. Writing a UI in COBOL on CICS is an absolute nightmare to deal with and maintain (not to mention my firm's egregious install and deployment process that is nothing but red tape and TPS reports). I'm working on a project right now where we're migrating some of our reconciliation screens to the web, where the UI communicates with a Java/Spring Boot server that itself interacts directly to the database using DB2 Stored Procedures.

In this space, I see a need for moving away from COBOL. But for the batch processing? Not a chance.