i don't think it would have much of an impact on wdw (we're in california)-but more and more school districts out our way (not our school thankfully) are increasing the winter break to 3 weeks. the reason being is that our hispanic population traditionaly travels to mexico over christmas and as a result their are large amounts of kids who no show the entire first week school is back in session. the schools don't get their funding for these unauthorized absences so they figured if they restructure the school year and give the kids a 3rd week off they are financialy better off. this is very controversial in one of our neighboring towns-the parents of the non hispanic kids are VERY upset because they point out that the extra week places a real hardship on working parents who may not have the ability to take 3 full weeks vs 2 weeks off to stay home with the kids, and the local daycares can't handle (or it's insanely expensive for the parents) a huge influx of kids for just one week.
we went to wdw in january a few years back-but i think our school calendar that year had us out right before christmas so we had that week after new years off and went then. i loved it-the parks were totaly vacant.