Corporate Death said something about it in an interview a few years ago. I'm hopeful it will be released, but then again they still haven't released the second part of Grim Scary Tales (not that I'm all that excited for that one, considering how mediocre the first part was).
its safe to say that they deviated from grindcore with each release. Gloom is for sure grindcore, but by the time Dahmer came out they were right on the border of death/grind - then once Murder Metal was released they were no longer grindcore.
Reprints of Sinister Slaughter on vinyl are available on Decomposed Records for anyone interested. Some on [url=http://www.ebay.com/itm/MACABRE-Sinister-Slaughter-NEW-2014-12-LP-death-metal-grindcore-CARCASS-EXHUMED-/331442530008?pt=Music_on_Vinyl&hash=item4d2b83a6d8]ebay[/url] ltd. 500!