Really? Assamites? Color me surprised.
They now share the Blood Sorcery Discipline with Tremere. Since we have Tremere, the Banu Haquim were obvious.
The last one should be social oriented. Toreador, Ventrue, Lasombra.
Lasombra would be nice, but Oblivion would be a Discipline just for them. All the Toreador Disciplines are already in-game, so that would be my guess. Either that, or Ventrue, as Fortitude won't require specific animations.
For example, Banu Haqim are linked to Tremere by Blood Sorcery, and Celerity is linked to Brujah;
All existing clans should have a unique discipline, like Obfuscate by Assamites.
We have Potence, Presence, Auspex and Dominate are unrelated with any playable clans. If we choose Toreador (Auspex, Celerity, Presence) as the last clan, there is no unique discipline for them. But Lasombra/Ventrue does have one unique discipline. Oblivion and Fortitude.
Let us separate what is feasible (the devs will pick the Clans that result in the lowest number of Disciplines requiring implementation, so a high overlap with each other), from what is desirable (for you, I take it, a combination of Clans that gives each a unique Discipline). FYI, V5 no longer has
any Clan-unique Disciplines. Serpentis and Vicissitude have been replaced by specific applications of Protean which is now shared between the Gangrel, Setites (now "rebranded" as Ministry) and Tzimisce, as opposed to being unique to Gangrel. Quietus and Thaumaturgy have been folded into Blood Sorcery, which is shared by Assamites and Tremere, each with specific powers. Obtenebration and Necromancy have been folded into Oblivion, which is shared by Lasombra and Hecata (re-united Giovanni and Cappadocian survivors), again each with specific powers.
Now, as to your desire for each Bloodlines 2 Clan having a unique Discipline, I doubt it is feasible in the long run. We presently have:
Brujah with Presence, Celerity and Potence
Tremere with Blood Sorcery, Dominate and Auspex
Assamite with Blood Sorcery, Celerity and Obfuscate
So yeah, a Lasombra with Porence, Dominate and Oblivion would leave Presence as unique to Brujah, and Auspex unique to Tremere, while a Ventrue with Dominate, Presence and Fortitude would leave Potence unique to Brujah and again Auspex unique to Tremere. But consider an incoming DLC clan (or was it TWO? I'm almost certain it was). Suddenly avoiding Discipline overlap gets exponentially harder.