“International language of the forthcoming generations will be solely and by necessity only a language of art.”

2000-09, Truth to Power, 2008

As quoted in Transnational Perspectives on Graphic Narratives https://books.google.com/books?isbn=1441185755 p. 5

Source: Karl Marx. The German Ideology. 1845

Though this has been quoted extensively as if it were a statement of Wittgenstein, it was apparently first published in A Brief History of Time (1988) by Stephen Hawking, p. 175, where it is presented in quotation marks and thus easily interpreted to be a quotation, but could conceivably be Hawking paraphrasing or giving his own particular summation of Wittgenstein's ideas, as there seem to be no published sources of such a statement prior to this one. The full remark by Hawking reads:
: Philosophers reduced the scope of their inquiries so much that Wittgenstein, the most famous philosopher of this century, said, “The sole remaining task for philosophy is the analysis of language.” What a comedown from the great tradition of philosophy from Aristotle to Kant!
Disputed

Source: Language: an Introduction to the Study of Speech

The Corruptions of Society, p. 9 (See also: The American Dream..)
The Corrupt Society - From Ancient Greece To Present-Day America (1975)

[O] : Introduction, 0.8
Semiotics and the Philosophy of Language (1984)
Context: A general semiotics studies the whole of the human signifying activity — languages — and languages are what constitutes human beings as such, that is, as semiotic animals. It studies and describes languages through languages. By studying the human signifying activity it influences its course. A general semiotics transforms, for the very fact of its theoretical claim, its own object.

Source: The Cultural Contradictions of Capitalism (1976), Chapter 3, The Sensibility of the Sixties, p. 131

Source: Eldest