Yes. yes, BUT i think developers should contact IGS in that case to make some changes in schedule - its simply counterproductive to have two same-game deals at same time/
That seems logical, but think about this way: if one game sale is moved, every dev needs to be contacted and bumped up one slot. Considering the sales are scheduled in one or two month blocks, that would be anywhere from 7-15 devs that need to be contacted. IGS can' just plop a random game into a "vacated" slot without a dev's permission. The best thing IGS could do is impose a clause of the contract that makes that once they sign the contract for the sale, they cannot schedule for the game to be bundled during that time period (and that is something that IGS wouldn't do unless absolutely necessary.
I suspect that for most indie game devs, some of the aspects of promotion (well the logistics and machinations that need to go on behind the scenes) are just not their bailiwick - after all, what they are good at is writing code and making games. And some of it is just completely out of their hands - for example, I'm sure bundle sites end up having to pull planned games all the time due to unexpected things like devs finding bugs or broken things, so if they have a game in the pipeline for a future bundle that is running well, they may need to add it in sooner to fill an empty slot. Just speculation on my part but it seems to make sense especially since IGS plans it's schedule so far out, overlap is bound to happen, especially with so many newer releases trying to get their share of the promo spotlight.