Hey James, thanks for the question! The legacy components will not be continually improved on as much as the upgraded components, so it's generally best practice to start using or switch to the upgraded components if possible to receive the component's newest features/improvements/bug fixes. To add on to @ScottR , legacy components are generally only removed when the upgraded component has received parity with the legacy component. We'll prioritize maintaining backwards compatibility and having an easy way to switch to the upgraded components so there should generally be no refactoring needed.
The upgraded version of modals is through Frames, but legacy modals will still be available for the time being!
Update (Nov 12, 2025): The Legacy Modal component is no longer available. The current version is now called Modal Frame.
Happy building!
Brenna