Okay,
We have two issues we need to decide upon.
1. The general results of the Toma alteration upon Keystone.
2. The other subplot that will be taking place at the same time as the Toma plot.
With this in mind, let's try and focus our discussion.
For the most part, I think alterations to Keystone should be pretty minor and ultimately inconsequential at this stage. (IE, 500 years from the alteration, little should be different from the pre-alteration timeline.) As Translanka suggested, perhaps Dorino (That was the village's name, correct?) hangs around instead of succumbing to whatever finished it off - however, I think the rise of a third power might be a serious long-run alteration. Maybe Dorino could survive, only to be usurped by Porre as time progresses. Thus, Dorino might serve as a Porrean outpost.
Nothing springs to mind right now for a second subplot.