Google CEO, Eric Schmidt, says that it will take them 300 years to index the world's information. Google has indexed 170 terabytes of data, and they estimate that there is a total of 5 million terabytes of information in the world. So Google has been around for 7 years, and they've done 0.000034% of the work meaning that the other 99.999966% will be done over the next 293 years? They obviously have a lot of faith in technology. But personally I think that it will be completed way before that at the rate google is going, I would not give it even 40 years.
Cheers,
Luke