If one knows their native language plus English, they'll have the vast majority of the world's knowledge at their fingertips.
And tools. For every mainstream app there's ten obscure apps that haven't been translated to your language. And other people interested in the same things you are. The Internet has made a vast difference here, dubs / subtitles / translations worked pretty well for broadcast and print media and international calls was rare. And I don't mean just chit-chats, go on eBay and the whole world is your marketplace as long as you pay shipping. There are so many other benefits to language convergence that you won't get through more translations.
There's really no credible competitor to English because there's no other big pairings. If you know two major languages it's likely Chinese/English, Spanish/English, French/English, Portuguese/English, Japanese/English, Arabic/English, Russian/English, German/English, Hindi/English etc. you just don't find many Chinese/Spanish or Hindi/Portuguese speakers. If you look at the EU it's quite clear that 94% now learn English and fewer people learn French and German, I don't have the numbers for Spanish or Portuguese but I'm guessing the trend is the same.
Sure it's always possible that English is locally going a little backwards like that Spanish is creeping up into the US but for the world as a whole there's no debate. Particularly since China as the only potential challenger has put huge effort into English proficiency, giving everybody else much less reason to learn Chinese instead. I know linguists hate it but I think that's misunderstood, if all you needed to know was your native language and English most can be bi-lingual. If you should learn your Amazon tribe's language, Portuguese, Spanish and English then it's for the few.