MangaCast's list of on hiatus/abandoned/canceled manga is interesting, and in places a bit sad.
While many of the titles are no big loss for not finishing, there's some real quality work scattered throughout the list.
We all know of course what a crying shame it is that ADV isn't publishing any more volumes of Yotsuba&! And I'd really like to read the remainder of Blue Inferior.
CPM's list is nearly as long as ADV's; I think they're out of the manga biz all together, so fans of the popular Slayers may never get to see the end of that manga.
At Dark Horse, both The Legend of Mother Sarah and Shadow Star deserve to continue; strangely enough, both Mother Sarah and 3x3 Eyes have both been abandoned twice, as they were originally being published in comic-sized floppy format back in the day.
DMP's abandonment of Bambi and Her Pink Gun is a shame, but not surprising given that the nihilistic manga had a hard time finding its audience. Maybe DMP will make enough money from their Yaoi lines to be able to publish a quality title with a low readership that can take the time to find its legs.
And then there's Viz. Even the premiere manga publisher can't seem to find an audience for many of its oldest titles, like Area 88, Bio-booster Armor Guyver, and Pineapple Army, which were all initially published in floppy back when today's manga kids were still in diapers. The real surprise though is that Rumiko Takahashi's Urusei Yatsura and Osamu Tezuka's Black Jack are on the list; when the works of two manga masters cannot continue, there is something deeply wrong.
All hope is not lost; there's always a chance that some of the missing titles may be continued, or even picked up by another publisher. This is what happened with the original abandoned manga title, Lone Wolf & Cub — after disappearing for year when First Comics folded, it was eventually picked up and finished by Dark Horse.
So let's all hope for a few resurrections!