Consider the following situation. Scientist A obtained a novel cool result and submitted it to a respected journal after putting the preprint to arXiv. The journal started the peer review process which will take 2 years. During this time scientist B drastically enhanced A’s achievements thus making them obsolete. B also put his preprint to arXiv, so the reviewers can easily access it too.
What will happen then? Will the journal publish A’s work? If not, why?
And what should A do to have any credit for his (pioneer) work?