There are a couple of other factors at play here. Further development will enhance Mammoth Mountain's marketing as a larger Summer destination in addition to Winter. It really is beautiful country, and although a 5 hour drive from L.A. it is a relatively easy drive (not a steep ascent or winding road) from Bishop, despite a base elevation of 8,800 feet and a peak elevation at the top of the gondola over 11,000 feet! Personally, I love skiing there.

Second, further development may increase pressure on the progress of opening the airport for commercial passenger service. The Los Angeles Times article linked in a previous post discusses this.