While I have yet to finish "The Man Who" series, and I haven't even started the Gap series, I've never been disappointed with the way SRD finished a set of books.
That being said, I have a very bad feeling about the way things are going here. The more I think about it, the more I come to the conclusion that one of two things is going to happen:
1) TC, still linked to the Arch (despite being 'alive'), comes to (or has already come to) feel that he is trapped as much as Foul is. Either directly (or indirectly through Linden), he acts to destroy the Land, thus freeing himself (and Foul, too).
2) Foul et al corrupt so much of the Land's essence and history that a correction or repair is impossible, and Linden decides to destroy the Land in a RoD to dwarf anything Kevin even imagined, hoping to form from the aftermass a new world of her own devising.
{3) Some combination of the above, possibly TC counseling Linden to make the attempt}
The title of the third book, Against All Things Ending, seems descriptive enough considering the cliffhanger at the end of the second. However, The Last Dark is downright frightening in its implications of how wrong things could go (think heat death, the result of entropy, etc).
After all, SRD has said something to the effect of, broken laws can never be mended completely...
