Composer shows "nothing to update" but there is a new version of the module I am managing a Drupal 8 site in Composer.  Commerce 2.0 was just released; I currently have 2.0-rc2 installed on my site.
This is my composer.json
&quot;drupal/commerce&quot;: &quot;^2.0@RC&quot;,

&quot;minimum-stability&quot;: &quot;dev&quot;,
&quot;prefer-stable&quot;: true,

To update, I ran composer update drupal/commerce --with-dependencies, which gave me this result:
Gathering patches for root package.
Dependency &quot;drupal/core&quot; is also a root requirement, but is not explicitly whitelisted. Ignoring.
Dependency &quot;drupal/core&quot; is also a root requirement, but is not explicitly whitelisted. Ignoring.
Dependency &quot;drupal/core&quot; is also a root requirement, but is not explicitly whitelisted. Ignoring.
Dependency &quot;drupal/core&quot; is also a root requirement, but is not explicitly whitelisted. Ignoring.
Dependency &quot;drupal/core&quot; is also a root requirement, but is not explicitly whitelisted. Ignoring.
Dependency &quot;drupal/core&quot; is also a root requirement, but is not explicitly whitelisted. Ignoring.
Dependency &quot;drupal/core&quot; is also a root requirement, but is not explicitly whitelisted. Ignoring.
Loading composer repositories with package information
Updating dependencies (including require-dev)
Nothing to install or update
Generating optimized autoload files
Warning: Ambiguous class resolution, &quot;Drupal\Component\Utility\Random&quot; was found in both &quot;$baseDir . '/web/core/lib/Drupal/Component/Utility/Random.php&quot; and &quot;/mnt/c/Users/x/d/mysite/vendor/drupal/drupal-driver/src/Drupal/Component/Utility/Random.php&quot;, the first will be used.
Removing packages services cache file:
/mnt/c/Users/x/d/mysite/vendor/drupal/console/extend.console.uninstall.services.yml
Creating packages services cache file:
/mnt/c/Users/x/d/mysite/vendor/drupal/console/extend.console.uninstall.services.yml
&gt; DrupalProject\composer\ScriptHandler::createRequiredFiles

So Commerce does not get updated to 2.0 (I already updated all the dependencies to their latest versions.)
I thought it might be a caching issue so I ran composer clearcache and then attempted to update commerce again, but I got the same result (nothing to update).
I thought it might be an issue with the composer module list being out of date, but Commerce 2.0 was released more than 48 hours ago.  So what can I do to get composer working in this case?
EDIT
My repo is based on the Drops 8 Composer repo from Pantheon, which is in turn based on drupal-composer/drupal-project.
Deleting the /vendor directory and running composer update gives me this error:
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

Changing composer.json to &quot;drupal/core&quot;: &quot;^8.4@RC&quot; &quot;symfony/css-selector&quot;: &quot;~3.2&quot; also results in the same error.
But, running composer install or running composer update drupal/modulename allows me to install the site and update individual modules (except Commerce) without any problem.
Thanks to @Neograph734 for pointing me in the right direction.

I needed to require Drupal 8.4-rc2 and drush 9, and then Commerce 2 arrived automatically.

Drush 9 appears to be a requirement for the 8.4 core update.