It is important to keep the best records we can of the various languages so that we can study the development of human culture.....it is NOT so important that all of these languages be retained by local cultures. Global changes make having an obscure variant as your first language a hindrance to progress.
(I do encourage them to keep up their original language and traditions if possible, though....it helps define who we are)
In another 100 years, I'd think almost everyone will probably speak one of about 5 major languages....the WWW/Internet will push this process rapidly.