The Wikipedia entry explains most of this https://en.wikipedia.org/wiki/Hiatus_(television) . Additionally consider the situation with Torchwood where the Indefinite Hiatus is generated by the producer/writer wishing to take a break..." In October 2012, Davies announced that for personal reasons the show would enter indefinite hiatus"
Currently we have such shows listed as Ended (which is not truly accurate) or as Running (which is just as innacurate). I suggest we have both designations so as to show a distinction between a break with an expected limited duration and one with no known end point.