So here are my current predictions for where the Safehold series is going to go with the next book specifically, and the series as a whole in general.
Okay, either LJ or Semagic is giving me crap, so i'm gonna try and split this up into two posts =P Part 2 should be immediately "after" this.
Obviously, SPOILERS, obviously
(And forgive the spellings please, since i haven't actually read the book. Some i've double-checked, others i'm just guessing on.)
Nahrmann will be brought back from the dead. At the beginning of the book Merlin instructs Owl to construct a brain scanner and a Class 2 VR unit that will be capable of supporting 3-4 personalities. Then in the middle of the book, while Nahrmann is on his death bed, Merlin shows up with a metal spiderweb helmet thing that he places on Nahrmann's head. He tells Oliviah that it will allow him to spend his last bit of time with her clearheaded and free of pain. He didn't say that was all it was doing however. Then near the end of the book while he's loitering about in Nimue's cave he mentions a couple personal projects he's working on, including getting the class 2 VR units set up and thinks "and at least one other possible use had occurred to him, although he still wasn't at all certain that one was going to work out." So at some point in the next book the VR unit will be powered up, and a copy of Nahrmann's personality just prior to his death will be booted up. So not only will Nahrmann be "back", but he'll be running on a VR mainframe where he'll be capable of running at faster than real time, and possibly be able to have direct digital access to all the information they collect, unlike Merlin.
At the end of the book they made a big deal about how important the result of the revolt in Sidermark's Hildemoss province was going to be. If Hildemoss falls, Sidermark may be screwed, and if Sidermark falls they'll have to wait a long time before another mainland realm will consider allying with them. On the other hand if Hildemoss stays loyal Sidermark will be in a good position to start a series of counterattacks, will probably ally with Charis, and will give them a foothold on the main continent, not to mention the kind of manpower they need to build a real army, and the chance to actually threaten the Temple Lands. I don't think Weber is going to screw both Sidermark and the readers over that badly by having the entire country come under the sway of the Inquisition and the Temple Loyalists and make everyone wait ten years in book time for things to start getting resolved. (Though it's entirely possible i'm underestimating Weber's willingness to screw over the readers =)
So i expect the beginning of "Midst Toil and Tribulation" will involve Charis' attempt to support Sidermark through the winter in general (that guess is a no brainer) and the events in Hildemoss over the winter and into the spring as it teeters on the edge of falling. I will be somewhat shocked, or at least disappointed in the protagonists' intelligence, if one of Merlin's "clones" doesn't end up popping up there to help stabilize the situation.
So in the grand scheme of things, i figure the situation in Sidermark as a whole will have stabilized by the end of the next book and they'll be able to start building up troops. Book 7 will involve the beginning of the invasion of the Temple Lands. Book 8 could reasonably involve the defeat of the Temple Lands.
Note that it's not impossible for the Temple Lands to fall in book 7, or possibly even by the end of the new book (and Weber _has_ been known to put the plot on fast forward at times,) but that's generally not the way to bet.
There are of course two potential "wham" factors that are certain to come up at some point, though not necessarily before the defeat of the Temple Lands. Either one could conceivably speed up or slow down the progression of the plot.
One: The power sources under the Temple. It seems likely the be either an AI or one or more PICAs. The question is what's going to trigger them and what they'll do when they wake up. If Weber wants to stretch out the conflict past Book 8, that's definitely the way to do it. Though it's also possible that whatever it is will "only" be the cliff hanger for the end of book 7 and resolving that will be the arc for book 8. (Of course the outside prediction is that since the descendants of Schueler were the ones who were told about it, and it seems like Schueler himself may actually have been an okay guy, that whatever it is under the temple is actually one of the other threads to the plot to actually _help_ Nimue. Not sure how much sense that would make in terms of the plot arc, but it would be funny for Clyntahn to figure out how to wake up the "Archangel" just as the victory of Charis seems to be a sure thing, only to have the Archangel turn to Clyntahn and tell him that he's been a very naughty boy =)
Two: The Gbaba. They're going to have to be dealt with at some point. Presumably the majority of that will be during the second part of the series (or possibly the third? I have no idea how many parts he's planning on doing.) However there might be a "scare" earlier with a scout ship that needs to be dealt with. (I should confess at this point that this idea is not something i came up with on my own, but something that was suggested on TVTropes.) This of course will cause Merlin to have to get out into space, reactivate one of the old ships, and kill the scout ship before it can report, and require them to put the technology effort on fast-forward before the Gbaba notice that one of their scout ships has disappeared.
It's also entirely possible that a Gbaba ship showing up could be the trigger that wakes up whatever is under the temple early. Or the actions of whatever wakes up under the Temple could do something with a big enough EM signature to catch the attention of a passing Gbaba scout.
But in any case, with or without the Gbaba the Temple Lands should be defeated "soon." 2-3 more books and 5 years, 10 at the outside, in book time. It seems likely that the thing under the Temple will have to be dealt with before that. I find it hard to imagine that after defeating the Temple that it would pose any significant challenge. Though i suppose it could wake up just as they're marching in, get the hell out of Dodge, and set up a resistance in some other part of Safehold. But it seems like the game would already have been pretty much lost by that point.
Speculation about how the switch to the next phase of the series will be handled is in Part 2 of the post.
Of course i think the only person who may see this that also reads Weber is steuard, and i seem to recall that he gave up on the Safehold series a long ways back :)