i don't see any disadvantages learning english. sure! we should still support our native language but learning a new one doesn't mean we are not patronizing our own. forgetting or discarding our own language is bad but not expanding our horizon of communication.
english is like any language and the only different is majority knows english than other languages.
in today's time, being a bilingual or multilingual is an asset on both casual communication with other people and as well as work related form. it breaks the language barrier easily so it helps both the receiver and sender to understand the message.
language is also part of education. limit your knowledge and you also have limited horizon of opportunities.