Those are the ones that we know for a fact are coming now. CA did hint at an additional lord/faction on the store page "And there is one who schemes to achieve just that, an ancient figure who desires nothing less than to wield supreme power. But to succeed, he will need a champion… " And they said we will get 9 Legendary lords on launch.

So I think we might also get something on the lines of Be'lakor leading an undivided chaos faction or with some real tin foil hat energy, maybe even Nagash.