I would like to continue the discussion about forthcomings, preprints and new editions we already started (e.g. https://pkp.sfu.ca/support/forum/viewtopic.php?f=25&t=13905). For us, it is important to know where OMP will go in that respect because a number of our plugins depend on how forthcomings and new editions are handled. We are mainly interested in how information is stored. The question of how information is presented (e.g. in the catalog, search, book page,...) is less urgent for us.
For forthcomings, we would imagine an input field in the catalog-monograph tab (that is, on the submission level). It might be a dropdown (with extentible options) or simply a checkbox "Forthcoming". If you say PKP will probably not deal with forthcomings in the near future, we would have to stick with our current work-around (that is, adding the string "forthcoming" to the prefix field in the monograph tab).
For new editions, we would start a new submission. The data wouldn't have to be stored (and collected) explicitly, if OMP would recognize editions of the same book via a key (e.g. author + title + series). But of course, collecting and storing the information explicitly would be much cleaner.
Have you discussed these topics any further and already know if/how you want to proceed?