An answer from a language acquisition specialist.
Negative or positive - take it as you will.
I would say that there is never a point where you
can`t learn a new language... However, it does become increasingly difficult with age for the brain to add new material to it`s language areas. This means that an older brain has to make do with the normal areas of the brain. By no means does this mean that you can`t manage well in a language, it just means that it will take a significantly longer amount of time for the brain to construct the necessary pathways for easy access.
A good metaphor often used is to think of the language part of the brain as an already built city, with public transportation - wide roads, clear signs, etc - all in place from the moment you`re born. It doesn`t take all that long to find your way around, and when new people (words, language, grammatical patterns) move in they`re immediately connected to the rest of the city - and your mouth. After a certain age (it varies from person to person), however, the "city" blocks immigrants.
However, this doesn`t mean that new people can`t move to the country (your brain). They`ll just have to work a little harder and forge a town for themselves out in the wilderness. It takes longer, needs more work, and will probably never be as easy to get around as downtown - but that doesn`t mean a new "city" can`t be formed. The brain will try to replicate the layout of the real "city" in the new version, so you`ll likely reference the layout you already knew in trying to find your way around - but things will never quite be the same and always take a bit longer.