I think that in some highly developed societies, and in particular in Scandinavia, this trend is actually good for endangered languages. The lingua franca of Scandinavia is English. The region, which is comparable in population size to a large German federal state or a medium-ish US state, has four different majority languages (Danish, Swedish, Bokmål, Nynorsk, all mutually intelligible, which increases the acceptance of imperfect language) and dialects play an important role for local identity. Of course, as a Scandinavian one has to learn one of these four languages to some extent, but the growing importance of English -- as a consequence of almost universal English proficiency and an influx of skilled foreigners not only to the capitals but also to the periphery -- narrows the gap between these languages and minority languages like Elfdalian and Sámi. As a consequence, the appreciation of the general population of language as a form of local identity also grows.