IMHO, this is the one baseball record that will never be broken, considering the way pitchers are used these days.
Interestingly, I began to reconsider this just a little bit a couple of years later in September 1988 . . . when Toronto's Dave Stieb took no-hitters into the ninth inning in consecutive games (he ended up with a one-hitter in both games), then started the 1989 season by throwing another one-hitter.