Well, Dark Eldar lost the Harlequin troupe last codex, so now I imagine that Craftworld have followed there, at least. That's the only real overlap I see between the three factions we have out, though I wouldn't put it past GW to come up with a Harlequin/Skitarii level Exodite force, too, finally. That would be cool. But yeah, I think it's not too far to say that's what they've done with Eldar factions, not what they might do with them.
Still, I think Daemonkin is a bit different since it's a subset of two other factions mushed together, rather than its own faction distinctly.
Interesting, making these new books more of a finer definition of the armies rather than their predecessors. I'd love to see an Exodite book too.
And I suppose Khorne Daemonkin more or less defined that God's armies rather than specified CSM or CDs. Bad example but you catch my drift.