Lae'zel
https://scryfall.com/card/clb/29/laezel-vlaakiths-champion maybe turns into Lawful or Neutral Good bcs her MtG-Card is white... (
https://scryfall.com/card/clb/146/shadowheart-dark-justiciar still black...) --> I would be very surprised if the color properties attributed by WoTCs / MtGs do not correspond to the facts... Exceptions confirm the rule...
Depending on how old Halflings can become, we could also meet Chaotic Good
https://scryfall.com/card/clb/55/alora-merry-thief again after about 100 years. Or she has a special explanation like Minsc and Volo why she is still alive after 100 years in exactly the same time and region...
Reunion with
https://scryfall.com/card/clb/156/viconia-drow-apostate and with the whole Shar plot, we just have to meet her again. She also looks very aged, which fits. Probably she won't be a playable companion, but rather the leader of the Sharrans in BG, to whom Shadowheart has to bring the artifact. At least that's how I imagine it.
Unsure about this one
https://scryfall.com/card/clb/102/vhal-candlekeep-researcher She could be an additional Wizard: Order of Scribes Neutral or Good aligned companion or just an NPC or there is a new Gnome Illusionist
https://scryfall.com/card/afc/16/minn-wily-illusionist companion.
Probably another Chaotic or Neutral Good aligned Ranger companion
https://scryfall.com/card/clb/269/cadira-caller-of-the-small or
https://scryfall.com/card/clb/230/erinis-gloom-stalker I would love to meet any descendant of
https://scryfall.com/card/clb/277/jan-jansen-chaos-crafter Possibly one Dragonborn companion of one of these:
https://scryfall.com/card/clb/280/korlessa-scale-singer &
https://scryfall.com/card/clb/281/lozhan-dragons-legacy &
https://scryfall.com/card/clb/295/thrakkus-the-butcher &
https://scryfall.com/card/clb/255/skanos-dragonheart &
https://scryfall.com/card/clb/188/livaan-cultist-of-tiamat &
https://scryfall.com/card/clb/90/renari-merchant-of-marvels Possibly Good aligned Kensei
https://scryfall.com/card/clb/290/oji-the-exquisite-bladePossibly a Yuan Ti companion, but more likely just an enemy boss mob
https://scryfall.com/card/clb/148/sivriss-nightmare-speakerAn alternative Rogue companion to replace Astarion I would really appreciate is Corans son
https://scryfall.com/card/afr/226/krydle-of-baldurs-gateHere I am unsure but I've heard she freed Minsc, so she could be around
https://scryfall.com/card/afr/138/delina-wild-mageAnother possibly Chaotic or Evil Tiefling companion
https://scryfall.com/card/afr/221/farideh-devils-chosen besides Karlach.
Possibly Neutral or an even Good aligned Necrolock
https://scryfall.com/card/afr/231/shessra-deaths-whisperPossible encounters with an entirely new adventurer party in the style of the former Drizzt Do'Urden adventurer party encounters:
https://forgottenrealms.fandom.com/wiki/Ellywick_Tumblestrum &
https://scryfall.com/card/afr/224/hama-pashar-ruin-seeker &
https://scryfall.com/card/afr/27/nadaar-selfless-paladin &
https://scryfall.com/card/afr/209/varis-silverymoon-rangerand / or
https://scryfall.com/card/afc/1/galea-kindler-of-hope &
https://scryfall.com/card/afc/2/prosper-tome-bound &
https://scryfall.com/card/afc/3/sefris-of-the-hidden-ways &
https://scryfall.com/card/afc/4/vrondiss-rage-of-ancientsPS: These are most of the characters that I either know from the predecessors or that don't mean anything to me and could be completely new or fit into the time frame of BG 3. I have not been able to check or verify every character 100 %.