How much it actually sacrifices now does depends on the plans until then, though. For a primary dark, there's the aforementioned Osiris in 2.5 months. And in 4 months (from now) there's the dark variant of Amaterasu. Then Pluto (yet another SSR) in just under 9 months (right before Set). Those are the 3 new possible additions that can move the needle for dark. Nyarlathotep (SR) is within a month and is pretty neat for an SR (I'm personally aiming to get her). But she's cool because of her A-frame atk and def debuffs; having Satan on the roster removes half of her gameplay appeal.

Ultimately though, it comes back to CaptainNoob looking over the gacha update schedule for himself, figure who looks worthwhile to aim for, and save jewels accordingly.