I have bought all the books since N3. Having all the art and lore in a book is just something I love having...(don't judge my piles and piles of gaming books in my attic). This is the first time I have wondered if there is even a point in collecting further as a Tohaa player. I doubt there is a single mention of the Tohaa in this book and I really am not expecting Tohaa to be anything more than a footnote in Infinity going forward. So is there any point in getting the books going forward?
Personally, I'm more concerned about space, because I don't have any more and it's impossible to remove a book without losing a piece of the lore, because all the books have a part of a faction's lore that isn't present in the new editions that follow. Paradiso has the story of the campaign that is only partially included in Deadalus, N3 has various things that are not included in N4, and N4 will probably have things that are not included in N5. Not to mention the fact that each edition very marginally retouches the old lore to add phrases or change terms. As for the question of whether it's worth buying the book, in principle you're buying for the general lore, there's no history codex in Infinity, apart from the Modiphius books. So there's no incentive to buy specific lore. Personally, I see the tohaa lore coming back in full through an N5 campaign book like Paradiso was, or Deadalus Fall with the Spiral Corps.
You can wait and see, logically some local warcor might have early access and you can see if the lore book is good for you.
According to the video they released. The N5 book is a LORE book ONLY. Detailing the new planet (Shinju) and where the various factions fit into it. Rules will be digital download only (no printed copy). Operation Sandtrap will have the same format as prior 2 player starters with a primer on the n5 rules.