The idea would be a "grand campaign" book, akin to The Great Pendragon Campaign, which would advance the timeline of the setting 25 years or so. So that's one button; I know a lot of folks don't like "advance the setting" things at all, and some do. (Please don't turn the comments into "advancing the setting is evil"; that's not the point of this post.)
However, it would be a bit different than TGPC, in that there would be several major decision points that the game master would decide upon at given intervals, either by his own fiat or by player intervention in the various plots and events that are boiling, and the outcome of each influences the outcome of the others. Thus, it turns from a railroad-type plan into a "choose your own adventure" book. That's the second button; I know a lot of folks have fond memories of "choose your own adventure" type books.
With two pages to describe the world-as-it-is on any given year in any given timeline, that gives a 200 page book, which is eminently doable.
The mechanics would work just like a choose-your-own-adventure book. In year 3, for instance, the game master is given a choice; if Iuz defeats the Shield Lands, turn to page 7. If the Shield Lands survive, turn to page 44. And then there would be more descriptions of how the world unfurls until the next decision point; if the giants, backed by the drow House Eilservs, conquer Sterich, turn to page 24, if not, turn to page 72. And so forth.
And of course if the game master just wants to have all the wars and politics and such going on in the background, as a backdrop to the player characters' actions, he still has choices and can have a ton of options for how his campaign unfurls over the course of time. There end up being 16 different outcomes with four plot-points. That can start to get a lot bigger as you start to add a fifth or sixth plot point or more than two possible results of any given plot point...
I figure that gives me the best of both worlds; it advances the timeline, but gives the game master a lot of choice beyond a single "Raistlin can't die in Pax Tharkas so he can be there later to stop Takhisis". If you want your player characters to influence events, you can, but if you don't, it's perfectly acceptable to let things just unfold in the background and keep them guarding caravans and exploring ancient ruins.
Also, please don't forget the Adventures Dark and Deep Bestiary Kickstarter going on right now! 900 monsters, suitable for most OSR-type games, all under one cover. Can you help get us to having an illustration for each and every one?