You're probably wondering where Rift Watcher 3 is.
Yes, Rift Watcher came out in December 2015 and Into the Rift came out in December 2016, but Rift Watcher 3 will not come out in December 2017. It is, in fact, finished. You might find it interesting to know it was practically finished before Rift Watcher was even published.
When I wrote the original story, it came out at 140,000 words, which is too long. (You can disagree with me, but it really is unless you're writing epic fantasy (I have, and it's 1,000,000 words long but that's a topic for another day.)) So I split Rift Watcher into three books: 40,000 going to Rift Watcher, 80,000 to Into the Rift and 40,000 went into the currently unnamed Rift Watcher 3 (which was going to be called Rift Watcher: The Last Edenite except some really big named franchise used a similar name recently and I'm not sure I want to follow in their footsteps.)
Anyhow, 40,000 words were added to book one, 80,000 words were edited into book two, and 40,000 needed to be added to book three. Turns out, it's harder than I ever thought it would be to re-end a book that's already been written. Small tweaks are made to the plot and big changes result. It felt like wading through molasses for some reason, possibly because other book ideas are pestering me. (Write me!) I did finally finish, coming in at 95,000 words (which is too long), and am currently sitting on it for an appropriate length of time before reading through it and cutting at least 5,000 words.
Unless I write a Christmas book someday, I won't publish again in December. I have my reasons, the main one having to do with momentum. December is the end, the closing chapter of a year, sometimes one that you never want to revisit, even in memory.
Publishing a book shouldn't feel like the end, but a beginning.