As an example of how overly optimistic people have been about translation, here's a page on Foresight Exchange (a long-running play-money prediction market) where people have been betting on the probability of high-quality machine translation by 2015, since 1995:
Even up through 2008, most people thought it was going to happen by 2015! Of course the people who were more actively following AI knew that it wouldn't. I probably doubled my fake money on FX, if only I could remember my login.
Overly optimistic over the course of 20 years is one thing, but I find it pretty difficult to believe that translation between major languages won't be mostly solved in 100 years. The difference between what is available today and 20 years ago is already pretty impressive, but 100 years ago we didn't even have the theoretical underpinnings of a computer, let alone a machine capable of any kind of automated, generalized translation. Unless machine learning developments or computing power comes to a screeching halt, I can't see any insurmountable roadblocks.
That isn't to say I agree with the sentiment that efficient and accurate translation will make English obsolete. Pretty much every major programming language, along with things like URLs and markup, requires using ISO Latin characters found on a QWERTY keyboard, which greatly limits the power of a major class of contenders. English just happened to be the lingua franca at the time that cultural globalization allowed for a language to keep that status long past the nation that made it such stopped being a super power (which, of course, may or may not happen to the US in the next 100 years).
I think translation isn't an isolated problem. I mean by that that we might not be able to solve translation alone, and probably will need an almost exact machine reproduction of the human thinking process to correctly translate something.
For any mildly complex concept, heuristics, context analysis, pattern matching and word databases won't be enough to match two exact sentences in different languages. Even a sentence like 'I felt sick watching him treating his partner this way' will need an extreme lot of intelligence to correctly parse and convey in a different language.
If in 100 years AI really reaches the holy grail and we have actual artifical intelligence, translation will be a solved problem. Now, will we be able to reach that goal in 100 years ? I hope, but that's not a given I think.
And the comments include "Google has been doing this for ages".
Siri, Cortana, Google Now, all have speech recognition. Google and Microsoft have translation engines. Microsoft and WordLens (and Google?) have live image OCR and translation.
It's no Star Trek Universal Translator, but it's a thing and it exists.
http://www.foresightexchange.com/fx-bin/Claim?claim=Tran
Even up through 2008, most people thought it was going to happen by 2015! Of course the people who were more actively following AI knew that it wouldn't. I probably doubled my fake money on FX, if only I could remember my login.