The good news is that Funcom has already linked existing TSW and new SWL accounts, so all you’ll need to do is log in to the Secret Worlds Legends account page this weekend using your TSW credentials and activate a legacy transfer (do not make a new account!). Players who do this will transfer any patron time to SWL, including lifetime subs, unlock every weapon page in the reboot, and copy over cosmetic outfits, pets, and mounts (with a few exceptions). Titles and achievements will not make the jump to the new game.
The legacy transfer system will remain available for players until sometime in August. Funcom still has not addressed what perks patron members will get nor an exact launch time for the headstart.
Source: Secret World Legends. Thanks to everyone who tipped this!
Update: Funcom has confirmed for us that emotes (like dances) do indeed transfer. There are things that do not, however, including the sleuth’s pipe, shoes of synchronicity, and Nassir’s dance.