I think the point is what language will the person think in if they have never heard any language in there life, theres million's of languages to express how you feel etc. i may be missing the point tho i dont really know.
i have often thought this believe it or not. they must just think in pictures..? another one is if you were born blind, what do you see in your dreams? or if you were born blind AND deaf what do you dream of at all?? some freaky shit