Here's some anecdotal evidence from my life:
I know 5 students who were radically accelerated. 2 went to Ivies, the other 3 went to very well recognized schools that were not Ivies (one for sure didn't go for financial reasons because his family was extremely well-off and the other two had full-scholarships). The two who went to Ivies I have not kept in touch with so I'm not sure about their success but the other three have gone on to top graduate schools (not Ivies either but top for their respective fields).
Also, DH and I both worked at an Ivy for some time (neither of us ever studied at an Ivy, though) and I only knew one student there who did her undergraduate at an Ivy, the rest were either from small well-recognized private colleges, state schools, or from abroad.
I've found in my field, at least, that connections/references/pure motivation leads much more to success than the school choice. I have a feeling that's probably different in larger fields like medicine/law/business where you just have a massive pool of candidates but in my field it seems to be the case.
