Depends on how the PG team decides to implement this feature. If they're OK with a virtual order (for "UI" purposes) while keeping the true order hidden then th

Depends on how the PG team decides to implement this feature. If they're OK with a virtual order (for "UI" purposes) while keeping the true order hidden then this would not require table locking (or it would be a very quick lock). If the order reflects the real / physical positioning then yes, it would probably require locking for a full table rebuild.