Saw your other edited thread "2015 HHMI waitlist." Why did you edit that one and stick to this one? I imagine you received your answer.
Anyway, in case anyone else has the same question and searches...
Correct, announcements have been made 3/20/15. If someone declines before the last deadline, sometime before April 3rd, which was when we were required to submit the last bit of formal acceptance paperwork, I think they go down their internal list and offer alternate students by email. However, that's pretty darn rare.
The only other scenario I can think of would be if someone had something happen, like an injury or family illness that would preclude them from conducting their research. However, with the insane amount of prep and planning, I don't think they'd award an alternate and would instead keep the funding for the following year and award it to an additional student.
If you're still curious, I'd suggest e-mailing the coordinator, whose email is available via the
website. If you have any other questions, I'm happy to help. I'll start an "Ask an HHMI Fellow" thread as we near August so incoming students have an opportunity to ask questions. I wish I had that when I applied.