That they did, on stream a few weeks ago.
As reported by @TheIdleOne ,
The situation is a bit murky around the new kingdoms currently, but I think the 505 acquisition of I+2 is enabling the devs to go forward with some wanted new localizations that they could not do previously, perhaps because of the financial costs of doing so independently. New localizations means new kingdoms. That and on the stream there was also discussion regarding providing the remaining missing hero(ine) racial classes, which would require new kingdoms to be released unless an unlikely rework of existing kingdoms were to happen.
They are much more likely to be faction-like in some way than kingdoms. Troops for kingdoms have to generally follow a rarity distribution scheme, which the one-off organizations do not follow (Primal, Apocalypse, etc.) Devs have commented about this in the past.
Although, The Vault might be a real possibility for a kingdom with the gnomes being common and Cedric as legendary. There are even pets present in the game files (which have been there a very, very, very long time) that could signal a kingdom, such as kingdom and racial pets (Not-so-Golden-Goose + Gnorman). There’s an awful lot of smoke signals pointing in this direction.