It's possible. We don't have any contemporary texts of Gilgamesh but we have extant inscriptions from contemporaries of him as well as a list of builders of a certain sanctuary that mentions him(although parts of the list could in principle be legendary). So it's not directly proven that Gilgamesh was a historical figure but the evidence we have doesn't contradict it or rule out the possibility either and I don't think anyone would be massively surprised to see actual evidence for him turn up.