In the can...

According to Marko, the next installment of the Frontlines* series, Centers of Gravity, is in the publisher's hands. It's the final novel of the series, wrapping up Andrew's storyline, although he says he isn't done with that universe as a setting.

It's available for preorder on BezosMart.

*Frontlines is the official name for the series, I guess. I call it the "Plural Noun of an Abstract Noun" series, which doesn't roll nearly as trippingly off the tongue.