People have been predicting that for a long time. I can remember reading something in Encarta 95 about it. But it's also been disproved for just as long. New dialect features are constantly being created, just as surely as old ones are levelled. Even as much as certain groups move around a lot, huge numbers of people are living in the same area their grandparents were born in.

(Sometimes, I feel surprised when I meet someone else who was born in the city I live in. But if I listen to how someone speaks, no matter if they're fifteen or fifty, I can tell whether they're from here.)