I keep hearing about these great new web part updates that we would like to use - pdf viewing in File Viewer and more information in the contact cards People web app. We are not in First Release so I don't know when to expect getting these features. Is there a way I can check if they will be rolled out to us soon?
The suggestion of the roadmap is a good one, especially now there are estimated release dates, so people can have a better idea when to expect features. For example 'SharePoint web part: File viewer' with support for PDFs, which is one you have mentioned, is expected by end of the year (or thereabouts!).
The Message center is also the place to track rollouts, though it can lack details sometimes, there are several entries for different web parts currently. The ' Updated feature: Web parts on modern SharePoint Online pages' entry mentions PDF support and also says the end of year delivery for standard users/tenants.