I think that dynamic languages played an important role in pushing for the development of mainstream static typing that didn't suck. ML's been around for a very long time, but there was seemingly little interest in pervasive type inference in languages actually used in industry until they had to compete with the concision of dynamic typing.
Actually building large systems in dynamic languages? Probably going to turn out to be a mistake though.
The maintenance burdens these languages are creating will make Cobol look like a kiddie bike with training wheels next to monster trucks.