I have just signed with Apress for third book about Linux. With two books now in the pipeline it looks like I will be busy for a while. I do not have definitive dates when these books will be on the shelf but my schedule calls for the writing to be completed by Summer of 2019 for the first and Autumn of 2019 for the second. These books constitute a two-book series.
As soon as I can post more information I will.