With cookies you can set the expire time yourself, as a developer. And looking at the list of the original blogpost from webkit (https://webkit.org/blog/10218/full-third-party-cookie-blocki...) it shows the following will be affected by the 7 day cap:

Indexed DB, LocalStorage, Media keys, SessionStorage, Service Worker registrations

Since cookies are not mentioned, I'm assuming it's NOT affected by the 7 day cap but will instead continue to work as normal (except for the fact that 3rd party cookies will stop working, which is a Good Thing)