In Japan, that is. Lupin III: Castle of Cagliostro will be released on Blu-Ray on December 3, and Series 1 and Series 2 will be released on December 12. There's no word on whether English subtitles will be included, but I sure hope so. There's no reason why not in this day and age.
It also goes without saying that a North American release would be absolutely fantastic. Nobody here ever secured the rights to Lupin Series 1; weirdly enough, it's the best and most famous of the whole bunch. You'd think somebody would jump at the chance to release one of Hayao Miyazaki and Isao Takahata's signature works.