Plugins can't move photos, so your odds are not good.
I mean, they could be moved on disk, then re-imported in Lightroom (at the new location), but they'd be new photos - edits intact, but edit history missing..
The old versions would then need to be deleted..
I mean #2, a plugin (or app) could use sql to modify a closed catalog, but that'd be the only way to do it "right" (without proper SDK support I mean), and I don't know of any such plugin or app.
I'd love to write such a plugin, and keep hoping for the support to be added to the SDK - fingers crossed..