Reading this gave me hope
http://n4g.com/news/881531/rockstar-still-has-other-projects-you-know
Plus, its R* second highest grosing games, so I wouldn't give up hope just yet, they still have 9 other studios with 2 that have helped in the development of the portable versions of MC3, and MCLA, plus in the article that the OP posted up, it says that they were working on one even after the development team walked, so there may still be an alpha version of the game floating around somewhere in one of R*'s studios.
P.S.Woot 500 posts!