I swapped to Fdroid Basic where they've been trialling many of the UI changes, today I reinstalled the main fdroid app and 2.0 was the default option, so no I don't believe theres any phased rollout.

If you're currently using a pre-2.0 version, you'll have to manually update the app, same as ever. From 2.0+ they default to auto-updating in the background.

I'm pretty pleased with the changes, especially search covering description etc and no longer just app names!