Learn a new language is always good, because every time you learn a new language if get access to a new world that was hidden from you, even if in the future we develop a technology capable of doing simultaneous translations of every know language, it will never be as good as to know the language that is been translated.
Nevertheless learning new languages is like make new friends and as having many friends, know many languages will probably make you do not spend the time you would like to spend in contact with the languages you know. That is the big problem that happen every time you learn a new language, inevitably you have to reduce the contact you have with the languages you know, with is sad because the best thing about learning a new language is to explore all the new possibilities that it give you.
To sum up, the problem that I have briefly discussed in this essay, exist not only in language but also in all knowledge. As you learn things, you start to realize that to learn new things you have to spend less time with what is familiar to you, with is not necessarily a bad thing, but is something to keep in mind if you value quality over quantity.