Generally speaking, English is the universal language on the Internet, but it has no official status, and it will never have. The reasons for the position of English are the imperialism and economical and political importance of English-speaking countries. Linguistically, English is extremely unsuitable for international communication, and the actual wide use of English tends to polarize the world into Internet users and Internet illiterates.
The position of English can only be altered by major world-scale political and economical changes, such as increasing importance of the European Union or a coalition between Japan and China. Such powers might wish and be able to promote a language other than English, possibly a constructed language, for international communication.
Alternatively, or in addition to this, the technology of machine translation may allow people to use their own language in international communication. Even if you expect the majority of your readers to understand your native language, you may be tempted to use English when writing e.g. about research work. Usually researchers all over the world know English and use it a lot, and often the relevant terminology is more stable and well-known in English than in your own language. Thus, to maximize the number of interested people that can understand your text, you often select English even if the great majority of your readers have the same native language as you. Alternatively, you might write your texts both in your native language and in English, but this doubles the work needed for writing your document and possibly maintaining it. The maintenance problem is especially important for documents on the World Wide Web - the information system where one crucial feature is the ability to keep things really up to date. Consequently, the use of English in essentially national contexts tends to grow.