Wren, I gave it about five seconds of thought - it will never happen. Besides, not all 10,000 ranking Yale first will be qualified applicants. So when you bring the top 20 or 30 schools into play, and there are only 30,000 kids at most with top 1% SAT and ACT scores, plus good GPAs, you won't have 10,000 "top" applicants at one college.
Won't happen though because colleges love to have tons of kids apply so they can be "selective" (single digit admission rate). There was an article recently about Duke's selection process. Half of applicants get tossed after the first read of the application. For kids without a major hook, the true admission rate of selective schools isn't 5-10%. It is more like 0% for half of the applicants, maybe 2-3% for some kids with slightly below average scores but something else special (great essay, really unique hobby, etc.) and somewhere in the 10-30% range for the top students.
Some of these top kids don't get into the top schools, because even 10-30% acceptance rates means admission is far from a given. So many resort to applying to 15-20 top schools in a shotgun approach. The result might be that some kids using this approach get into a number of the top schools. Some other kids don't want to use this shotgun approach, apply to maybe 3-5 top schools, and don't get into any.
The kid using the shotgun approach can't attend the 5 top schools to which they were admitted (and they may not even like the schools) - maybe they effectively "took" the top spots from some other kids who only applied to their true top choices. If there was a way to figure out the true top choices of the top applicants, perhaps there would be fewer disappointed kids come April 1st. Sure, there is ED at some schools, but family finances figure into this, so ED is not a good idea for all.
