Probably some kind of small xp boost like 10% for an hour everyday. Jagex want RS3 players to grind less with the wellbeing initiates anyway. The probably-nots highly likely include exclusives 60 minutes of Pink Skin per day or 60 minute of access to beta server.
I'll say whatever benefits from the new aura probably can be obtained from other means in a few months, if not now.
Gives you a 10% increase to XP with a chance to increase XP by 100% Duration 30 minutes Cooldown 23 hours 30 minutes
It's already ingame apparently
Yes, some tiny xp buff. Really not surprising as giving up xp and level to reduce grinding is pretty much the meta of the entire video game industry now. At least Jagex is not locking exclusive content behind these promotions.