All versions of ClassicPress including 1.0.2 are automatically made available via composer once we release them: classicpress/classicpress - Packagist
My guess is you have "classicpress/classicpress": "1.0.1" in your composer.json file. composer update will only update dependencies within the version range specified in your composer.json, it will not change the version ranges itself.
You can change that to "classicpress/classicpress": "^1.0.0" and run composer update again. This should pull in 1.0.2 and any future 1.x versions as we release them.
Or, if you don’t want to start using a version range, you can always run composer outdated to know if there is a new version available, then in this case composer require classicpress/classicpress:1.0.2 will get you the new version and update your composer.json accordingly.