Because I am an expert on Oracle development tools, I'm often asked for advice on technology migration projects, typically from Oracle Forms. Most of these projects originate in the IT department, and they often fail the simple test of business justification. Simply: Does the benefit justify the cost?
The maximum achievable benefit is limited by the difference between the current technology and the proposed new one.
Changing your application from Oracle Forms to Oracle APEX has a short technology distance: From one PL/SQL based, data-driven monolithic application to another. The only difference is that APEX will run in a browser without the Java plugin, for example in mobile. Because the technology distance is short, things can't change much and you can't justify much cost.
Changing your application from Oracle Forms to Oracle ADF has a longer technology distance: From a PL/SQL based, data-driven monolithic application to a Java-based, UI-driven, modular architecture. The technology distance is much greater, meaning that you can do completely different things with an ADF application than a Forms application. The potential upside is much greater. Whether you are able to realize it is a different matter.
Yes, the projects originate in the IT office, but it is typically the business that is chasing IT for a long list of enhancements. Many Forms applications started off life by being created by what is now known as 'citizen developers'. The applications were wrestled back into IT and managed. Sadly, nobody is leaving college with Forms skills and the old school are taking retirement! Yes, Forms is supported out until 2020 and probably beyond. Many Forms apps are critical to businesses, they have successfully grown to handle complex business processes. So, what is IT to do? Outsource the Forms to a competent supplier; hope that no changes are required as there are no skills to make the changes or consider a rewrite or retirement. Whether you choose APEX, ADF or the plethora or other development tools the age old problem of business justification raises big questions. I like the idea of 'Maximum Achievable Benefit', I am sure a large consultancy may adopt it as a new methodology, or perhaps it exists already. Great to see you raise the issue, though doing nothing is a difficult choice, especially on the day when new features come out in ABCS,,,