[Paleo Conservative]

The trick is, someone has to come up with a COBOL compiler for Linux.

Wouldn't it be better to cross-compile to new C or Java code? I think I read somewhere about a program that takes original COBOL code, analyzes how various parts of the code interact with each other and creates new source code in C with documentation. Supposedly it can even recognize dead code that is no longer referenced and delete it from the new source code.

[Tokhtamish]

First you have to ramp up the existing legacy support staff. Converting everything to C means, essentially, a whole new system to learn for them. It would be a matter of phasing in the C code when the legacy maintainence people retire.

Around 1980 a huge number of mainframe programmers lost their careers and had to find something else to do for a living. They were never replaced.

[Frumious Bandersnatch]

One of the biggest problems is the lack of original source code...