I am missing your point; the people running UT have the 10% rule in place to achieve the exact opposite effect: to increase diversity within the student body. Therefore, I believe you mean to say that anybody BUT whites would disappear, i.e. black/hispanic/<underrepresented minority>.
Unless, of course, you are implying that the 10% rule attracts whites, somehow.
While I have witnessed the 10% rule opening doors for many students -- as a hispanic student, many of my hispanic peers would simply not have had the opportunity of a first-class eduction -- I don't believe a general universal rule is the answer, but, rather, admissions should be examined case-by-case.
I think the real point of the 10% rule and rules like it (here at KU it's a 20% rule), is to make the college decision really easy for those desirable top-of-the-class students. Hell, it worked on me. I was #2 in my HS class, and the fact that I was automatically accepted (and offered scholarships to boot) really made me not want to bother with a real college search. I had better things to do (or so I thought at the time) my senior year than tour colleges and figure out financing.
Think about it. The average state school is not going to be attracting a large population of out-of-state students. Here at KU we attract many for our Journalism/Social Welfare schools and our Med School Campus, but the vast majority are from Kansas or Missouri. It is in the University's interest to try and lock in the local HS talent as soon as possible, before that talent has the chance to look at a brilliant school in California or Boston. Without such rules, said local talent would be less likely to stay local, and state schools would have an even higher ratio of drink-yourself-retarded students to academic all-stars than they already do.
Unless, of course, you are implying that the 10% rule attracts whites, somehow.
While I have witnessed the 10% rule opening doors for many students -- as a hispanic student, many of my hispanic peers would simply not have had the opportunity of a first-class eduction -- I don't believe a general universal rule is the answer, but, rather, admissions should be examined case-by-case.