A minor correction: Grim Fandango used the GrimE engine, not the SCUMM engine, and it doesn't work with ScummVM.
However, ScummVM's sister project, ResidualVM, was created to do for the GrimE engine what ScummVM did for the SCUMM engine, so you can still play the game on modern OSs without too much hassle.
The likelihood of Lucasarts classics ever being re-released is miniscule, since why would Disney put effort into putting out The Dig or even Monkey Island when they could make ten times as much money from Star Wars?
However, ScummVM's sister project, ResidualVM, was created to do for the GrimE engine what ScummVM did for the SCUMM engine, so you can still play the game on modern OSs without too much hassle.
The likelihood of Lucasarts classics ever being re-released is miniscule, since why would Disney put effort into putting out The Dig or even Monkey Island when they could make ten times as much money from Star Wars?