2003:5.3.5/6 says about delete[]:
The delete-expression will invoke the destructor (if any) for the object or the elements of the array being deleted. In the case of an array, the elements will be destroyed in order of decreasing address (that is, in reverse order of the completion of their constructor; see 12.6.2).
So if your std::vector object's allocator uses delete[] then, yes, it is bound to destroy elements in reverse order.
However, there is no guarantee that your std::vector will work this way (and, in fact, it most likely does not), and I can't find any citations specific to the container.
Really, I think it's all down to your allocator and 2003:20.1.5 (which lists the requirements placed upon allocators) doesn't appear to say anything about it.
