At the rate man has been using natural resources there might not be a planet earth for the next generation. However, this prediction will not be realized if there is a way for the self-destruction countdown to be reversed.The preceding sentence is, technically, not a prediction. (It uses "might not".) However, I think the sentence in question (in bold) is OK.
Has mankind unleashed a bomb which could fulminate within the next decade? Or are the supporters of this theory being pessimistic for no apparent reason? In the second sentence, the phrase "for no apparent reason" could be replaced with "for no good reason" or "without justification".