And still anyone with the skills could implement a javascript client. If ethereum really breaks through there will be a lot of opportunity for new development. I think its a good thing to see there are already multiple prototype clients in multiple languages.
They deliberately chose to develop multiple clients in multiple languages reasoning that a single client could be a point of failure i.e. if only one client was used and it faced problems/bugs in future it would effect everybody. In this scenario its impact would not be so utterly complete.