Hello Sandy,
Well at the very least you should consider upgrading to version 10g or 11g of forms which are web based (forms become web enabled @ 9i) before migrating to a different technology (java, adf, apex, etc.). The reason for this is that you stated the application is fully functional and that you planned on using it for 5-6 more years.
Upgrading to 10g or 11g is the most cost /time efficient way to modernize your application. Depending on the size and complexity of your app, migrating to a different technology can take long months or even years to migrate...
No matter what you may hear, Oracle is committed to continuing the development and support of forms (read their statement of direction here:
http://www.oracle.com/technetwork/or...d-3-129969.pdf). Many organizations are in a rush to get off of forms because they think they have to and are not moving away for the right reasons. Many dollars and man hours have been wasted.
My company, PITSS (
PITSS - Modernization Experts Oracle Forms to ADF, APEX, Java) is an Oracle Partner specializing in Oracle Forms modernization. If you have more detailed questions we would be happy to recommend solutions. And believe me, my responses above are totally neutral because we help clients upgrade/migrate to whatever they want so there is no additional benefit to me if you decide to stick with forms.
I hope I was able to bring you some clarity to your situation.
Best Regards,
Jason Marra