Most of the languages knew today slowly are disappearing. This phenomenon could be beneficial for some part of the population or maybe not. In my opinion the fact that something does not exist anymore is, per se, negative especially when the topic talk about a cultural, ethnic and historical thing like a language of some population.
Firstly, arguing about a population if the language is dying this mean also that this people are extinguishing from the earth signaling obviosly something not good. Secondly, the culture of those people is preserved indirectly in their communication abilities – through the language people communicate and pass over generations customs and traditions that form the culture. Losing this culture is a bad thing for everyone. Lastly, if some language disappears is most likely to be some sort of language that is unknown and for sure it is not necessary to learn it, for this reason there is no possibility to argue that the disappearance of this one could be a positive thing for people everywhere.
As far I am concerned, every time some language, culture or ethnicity are dying there is something bad about it. There is no possibility to imput at this phenomenon a positive effect.