With the greatest respect to everyone's opinion, especially the preservation minded, there's at least 3 C16's that I can think of, and I'm not a particular fan of the Rio Grande.
There's one being restored in Utah, and one on display at Gunnison. Will there ever be a requirement for more than two operating C16's?
Right now, worldwide, we are seeing what is likely to be the high point of railway/railroad preservation. We are seeing "impossible" projects being completed at a rate we could never have imagined thirty years ago, but the fact is we are all getting older, and younger generations who never knew a railwayman grandfather, and are several generations removed from riding the train to school or market day, they just don't have the interest. Will they be interested enough to spend time working on old trains. Or vacation dollars taking their kids to ride a train when trains have no actual relevance in their day to day lives.
I doubt a
need for 278 to be operational, but I do see a worthwhile role reminding the non-enthusiasts that the Rockies were first tamed by the narrow gauge.