I'm surprised that this thread has been allowed to continue. Serif/Affinity are obviously not in the software business as a hobby - it is a business and no doubt like any business is intended to show a profit.
That being the case, there's no doubt in my opinion that the developers will introduce new features, etc on a soon as possible basis as there's every incentive for them to do so. If, although I very much doubt it they manage to find a way of opening INDD files directly with Publisher then so be it although as that file format is constantly, or so it appears to me, to be a moving Adobe target it will be a no go in my book.
IDML - well maybe but going on about it day after day isn't going to make it happen any faster. Publisher is what it is and for now that's what it is.