Some of those developing AI technologies will undoubtedly want to supplement their own capabilities. Given that, there will arguably never be computers that are "smarter" than at least some humans. So this seems rather like a non-question, except to the extent that such enhanced humans would themselves pose a risk to humanity at large.

Also, if and when strong AI develops, only such enhanced humans will remain players. Unenhanced humans will at best be pets. This is O. B. Hardison's thesis in Disappearing Through the Skylight: Culture and Technology in the Twentieth Century <http://www.amazon.com/Disappearing-Through-Skylight-Technolo....