Is preserving languages a good thing?

[no one]

Extinction, in all of its forms, is immune to any human endeavor. Language is an evolving entity. The English spoken in America today, is not quite the same language as it was 50 years ago, nor is that version the same as it was 50 years prior to that. The more humans intermingle, the more cultures fuse, the more homogenized communication between them becomes. More than likely, there isn't anyone alive today who will live long enough to witness the Spanglishization of all human communication, but that day may be on the horizon.