This is a pedantic point, but Bitcoin forks happen frequently as part of the blockchain design (see https://blockchain.info/orphaned-blocks for around 20 forks last month). The only differences for the August 1 event are that the fork will be given a name (Bitcoin Cash), and that some people will be running modified code that doesn't care if its fork is shorter than the main chain. Observing that the fork will exist isn't the important thing. It's whether anyone will care after a week or two.

People are using 'fork' to mean 'multiple branches of the blockchain are considered authoritative', not 'multiple branches of the blockchain exist in an immediately-abandoned state'.