Planning some wiggle room

As I polish up a short story for contest submission, I find myself in a world building dilemma.  I know that the story is just the first step into a future series I have planned, and all parts of the series will need continuity between them.  The main framework and details of the universe are worked out, but are not on the same level of detail needed for a novel.  It’s hard to project into the future to see what little fly-away details in the short story will hamstring any later world building for the series as a whole.

Of course, a contest submission won’t necessarily be published, and most continuity points can be ironed out later when I have more time to flesh out the universe.  In any case, how do you deal with this problem?  Are there any main world building issues that you make sure to develop first, or others that provide a little wiggle room if something needs to be changed later?