IMO it will be ruby. Between the readability and "fun factor" involved in writing ruby and the robust web frameworks I see ruby dominating at least in the startup scene. Fast development and iterations without a lot of baggage.
Truth be told, i doubt there will be one language dominating anytime in the future. Thats the point of different languages, that they are good for different tasks. But as fast and general estimate I would say ruby in the startup community.
