We've seen A LOT of loa this expansion which have been pretty cool, though a few got shortchanged (Shadra got robbed, so did Hir'eek but hopefully we can bring them back)
For old loa... We see Shadra in Zuldazar, and Hir'eek in Nazmir, but Shirvallah, Bethekk, Hethiss, and Zanza don't show up outside of passing references in the hall of Loa.
Of new loa mentioned, only Torcali, the Direhorn loa doesn't appear anywhere in questing.
Shirvallah: Tiger loa, shows up in Rastakhans rumble in hearthstone as a paladin loa but uses Kimbul's art in it, making some folks wonder if they're siblings lorewise.
(Oddly enough, lorewise Kimbul is supposed to be a tiger with black fur and blacker stripes, but I guess that'd have been tricky for Blizz to do as a model)
Bethekk: Panther loa, sadly hasn't shown up since Cata-ZG which portrayed her as taking direct control of her priest.
I expect Shirvallah and Bethekk don't show up in Zuldazar because there's not many Tigers and panthers there. (Sadly no jaguars either despite the mesoamerica look) It's actually kind of odd that Kimbul was chosen to show up given he was pretty minor but I think he was chosen since he showed up in the "Traveler" book recently.
Hethiss: In the past Darkspear were implied to consider the snake as a pretty important spirit (Snake totems, a quest in TBC showing they disdain birds and consider them more a forest-troll/amani spirit and like snake spirits more, etc) but sadly he hasn't shown up in any quests at all since Cata ZG
Hard to think of a way to bring him to play in BFA but here's hoping we get to see the Darkspear set up some shrines to him.
Torcali: It's actually pretty odd we haven't seen Torcali as she's implied to be a defender of the Zandalari's homes, deity of the harvest, shield, etc...
Hopefully if the Naga or someone else attacks Zuldazar again after battle of Dazar'alor Torcali can be summoned and we can have her drive them back into the sea, or perhaps we get a questchain explaining their absence (Maybe Torcali was weakened in some ancient battle or Torcali powered the shield that protected Zuldazar during the Sundering?)