Not to be a party pooper but.....
Paretos Principle does not actually state "you can get 80% of the result from 20% of the effort".
It states that "80% of your results will generally come from 20% of your efforts".
The difference is subtle but very important in this particular case. Taking 2000 hours worth of practice as the benchmark, the first is incorrectly stating Paretos Principle to claim you could reach 80% mastery from that 2,000 hours practice. The second is saying that whatever level you reach from that 2,000 hours worth of practice, will come from 20% of the effort expended during that 2,000 hours.
Having said all that, if you devote 2,000 hours of dedicated practice to something you will very likely reach a pretty darn good level, if not 80% of mastery. It must be said too, reaching even a "pretty darn good level" at something is a whole lot better than being 2,000 hours better at watching tv.
I agree with Bob W, 2,000 hours of language practice would get you well above conversational fluency level. I'd also suggest Kung Fu as being totally awesome for many reasons and 2,000 hours of training would see you well on the way to a black belt or higher. :)