That would not be a wise bet
Moore's Law also applies to chip fab plants. It now costs almost a billion bucks to make one fab plant producing chips with a speed of 3 GHz. Intel and AMD are not making as much money as they previously did. Based upon simple scaling, an 18 GHz chip would require a 6 billion dollar fab plant. Intel's total cash is $ 14.82 billion. Is Intel willing to bet almost half their total cash on a new fab plant? Is the market for super fast chips strong enough that they'd recover their investment? I don't think so.
Gary