Do you have any knowledge if another Kuroshitsuji major-minor character is fated to die in the manga, and whom it is?
I’m pretty sure both Phantomhive twins are bound to die sooner or later by the end of the series.
As for the rest, I’m not sure (now that Agni is dead, we know that no one really is ‘safe’ in this
manga, so technically, every character - be it a regular or a minor,
popular or unpopular character - could die), but I can imagine that the servants (especially Tanaka), Undertaker (he’ll probably die dramatically like Snape in HP) and the Queen & John Brown (in case they are the main villains) will die at some point in the manga. And Blavat, too (he’ll probably be killed off by the true ‘mastermind’ of the sect by the end of the current arc).