And will also be a new tera abuser to boot, and can pass wishes around. Will probably help a little bit with the not very fun meta but a tera test soon after the dlc drops is definitely warranted at this point.
Also on the topic of drops from ubers, I expect Volc and maybe a shaymin-sky quicktest. (on the merit that covert cloakwill make it easier to deal with, even if it ends up going back to ubers like it probably will.) I don't expect anything else to come back until either dlc 2 or if tera gets banned
Clef really likes being a Fairy type, and there's not a ton of steel or poison moves being thrown around as coverage right now so staying a fairy is pretty safe. While it can certainly make use of tera in specific matchups, what makes you think it'd be a team's preferred abuser?
Also, Shaymin-Sky is staying Ubers as long as it has Serene Grace. Seed Flare is disgusting, and there's two OU proper mons that can outspeed it naturally: Dragapult and Zamazenta. The only OU-viable mon in lower tiers that outspeeds is Barraskewda, who can't revenge kill a healthy Shaymin-S.
252+ Atk Choice Band Adaptability Barraskewda Liquidation vs. 0 HP / 4 Def Shaymin-Sky in Rain: 277-327 (81.2 - 95.8%) -- guaranteed 2HKO
Scarf and Booster Energy mons can outspeed, but then they're risking a -2 SpD on the switch in, forcing them right back out if Shaymin-S switches out for another special attacker. Covert Cloak users need to deal with 120 SpA and 120 BP on Seed Flare, and you can't out-bulk Seed Flare because Seed Flare + Serene Grass is a fair and balanced combination, so even Eviolite Chansey needs to pack a grass-resistant tera type to avoid a 2HKO at -6 SpD.
Shaymin-S isn't a great Uber because 100/75/75 is bad bulk by Ubers standards, but in OU that's a bit better than Dragapult, so the pixie can stay gone.
(All of that is without going into Air Slash flinch hax, so even if you think you have a counter, you don't.)