Nothing at all may happen. If you’re lucky, a few readers may write to you – expressing interest, asking questions about your sources and methods, perhaps disagreeing with you. Mostly, though, readers read and digest on their own. Very occasionally, someone will be so moved to disagree that they write a response. If the journal decides to publish the response, they will normally give you a chance to supply a ‘rejoinder’. Though it is never nice to be disagreed with so vehemently, you should take it as a compliment – and a sign that your ambition to say something important has succeeded. No-one ever writes a response to an insignificant paper.
Nowadays, journals know how many readers your article is getting (it’s an ‘article’ now that it’s been published, no longer a ‘paper’ or a ‘manuscript’), because they collect download statistics (from their own site, and from ‘archive sites’ like JSTOR which may start holding your article after a few years). You will probably never know this yourself. But you will know something about the impact that your article is having from the number of times it is cited by others in their own articles and books. Unlike in some of the sciences, the assessment of impact by citation is a very imprecise matter. In history, research doesn’t cluster around a set of ‘hot’ issues; there is no clear ‘cutting edge’ of research.
We work across a much wider range of themes, driven by our own curiosity and imagination as well as by the historiography, and sometimes it takes many, many years for others to wake up to the value of our research. For example, one estimate by the British Academy is that while half the reader-downloads of biomedical articles take place within two and a half years of publication, half the reader-downloads of historical articles take place within five years.
Furthermore, we make much more use of archive sites like JSTOR than do the sciences, and it takes twenty years for the average historical article to receive half its reader-downloads on JSTOR. In other words, just because only a few people have read your article within the first couple of years of publication (and perhaps no-one at all has cited it!), doesn’t mean that it won’t be widely read (and cited) in a decade. Did we mention that history moved slowly?