It is an indefinite suspension that will last a minimum of one calendar year, meaning Randy Gregory can apply for reinstatement on November 6th, which is 60 days prior to January 5, 2018, the one year anniversary of the latest suspension.
If Gregory has complied with the terms set forth is his suspension, no failed tests, no arrests, went to treatment sessions/counseling, etc., the medical director and medical advisor in charge of his case will make a recommendation to Roger Goodell on the player's request for reinstatement.
Goodell can then decide if he thinks Gregory can return to active status.
All parties involved are supposed to help Goodell make his decision within 60 days of the receipt of the application, but there is no deadline for an announcement. It happens when it happens.