At my office, we are about to embark on an epic journey of converting an old Delphi 5 application to something more modern. One of our options is to convert to Delphi Prism, but we want to see what options are available to help us. So far, all I've found is Oxidizer (last worked on 2 years ago). Are there any other options for helping us convert reasonably quickly to Prism? Thanks.
As many comments suggest and encourage, rewrite, yes. Why? Many of those reasons have been mentioned in comments, notably the declining degree of direct language and tooling support, 3rd party component support, but also not mentioned is a decline in available talent to keep the ship going. It is the same problem that many of the mainframe era and direct derivative projects face: talent and interest in those types of systems is waning.
One of the biggest challenges for a migration effort isn't what language or platform or toolset to go to, especially today: there are lots of good options, some better than others depending on what one is trying to accomplish and expect from the resulting effort. Today the biggest challenge, as it has been for years, is finding the right talent to translate the old system into the new, or at least translate it well enough and efficiently enough for others to build in the new.
In the OP's case, it sounds like that they have not only skilled practitioners in not only the legacy language and tooling, but also to a degree are highly familiar with the customer and the domain. That is a big advantage.
What I suggest, based on my experience with genuine legacy migration projects, is take a bigger jump while there is expertise on the originating end. It becomes monumentally harder when those builders and maintainers leave.