7000 BC would have been Semitic still, right? The Akkadians moved into Sumeria around 3000 BC, but were they in Canaan in 7000 BC? or were these people Hurrians?
None of the above; the Sumerians (by their own account) arrived from the sea, as immigrants from somewhere (perhaps the Indus Valley or elsewhere in India), and the placenames they used for rivers and cities were borrowed from the previous dominant population; the only trace of that lost language consists of those placenames preserved by the Sumerians. While not the earliest writing system, their cuneiform is the earliest writing system that can be read. These masks go back to those unknown people, or (as seems likely) their unknown neighbors.
The Semites appear to have come from Africa, based on the distribution of that language family (nearly 400 million speakers of Afroasiatic languages, most of them Arabic speakers; as you noted, Akkadian is an extinct Semitic tongue, as is its descendant Assyrian tongue, ancient Egyptian, ancient Aramaic, etc). It is not unlikely that the people who made these masks have living descendants, but the culture (and probably the language) is long gone and forgotten, as well as unrecorded.
http://en.wikipedia.org/wiki/Afroasiatic_languages
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