What should we learn, English as a lingua franca or "formal" English?

In my opinion, I think we should still learning English as a lingua franca because as we try so hard to learn a language that is not our mother tongue, we are overlooking what is related to speak and use our own language better. Also, I think that as we are getting so deep into English language world, we are losing our own cultural diversity; we are turning ourselves into an English native-speaker way, with all their traditions and customs.

 Moreover, if we get to that point, we would lose a principal feature of our world in general, that is related to cultural diversity. Finally, I think that as speak English is a trend in population these days, in a decade or two, maybe French will be the global language, or maybe German, we don’t know but we’ll have to be prepared and not only focus in one language.