It seems very likely, that a new DLC will be released in the near future.
There was a new beta version of MoM released a few days ago:
https://steamdb.info/app/478980/depots/
And there is also a new (still hidden) DLC entry listed:
https://steamdb.info/app/478980/dlc/
I hope we will hear something official soon
Just for reference:
The first DLC was added to the list on November 14th 2016 and was officially released on December 21st 2016 (about 5 weeks).
The second DLC was added to the list on July 11th 2017 and was officially released on August 3rd 2017 (about 3 weeks).
If they follow this pattern with their third DLC (which was added on August 21st 2018), the release might be between mid September and the beginning of October.