I am fully expecting one of the first codex releases to be one for Primaris Space Marine chapters. This would include a lot more units that we have not yet had hints for, apparently except for in the Dark Imperium Novel...... which hints at Repulsors, Repentors, Reivers, Aggressors, Overlords, Librarians, and Apothecaries for Primaris Marines. And of course the Redemptor Dreadnought
Here are the conversations that give us hints on these.
the full conversation