Welcome to cruise-chat!
What the arrival time means is that the ship should be tied up at the pier by 7am - it is often a bit earlier than 7am. It doesn't mean everyone leaves the ship at 7am. In fact, no passengers will be leaving immediately. The Customs and Border Protection officials will have to be set up to accept the passengers, luggage will need to be moved ashore, etc. When you leave the ship depends on several factors. If you choose to do self-debarkation then you'll be the first group to be called to leave. Self-debarkation means you can carry all of your luggage off the ship without assistance. This group is usually called to leave within an hour of the ship being moored. If you can't do self-debarkation, then your luggage will be transferred to the terminal and you will be called off the ship based on when your flight home leaves. It is typical to see a group called to leave every 15 to 30 minutes. Earlier flights get priority to leave, later flights mean you are in the last groups. It is usual to see the ship emptied by 9:30am or so, although circumstances can cause delays.
I get up early because I like to watch the ship's approach to the pier. I suggest that you do plan to be awake by 7am. They usually ask passengers to vacate cabins by 8am, and move to a public area to wait. And yes, they will serve breakfast - both in the buffet and in the main dining room. I strongly suggest you eat in the dining room on the last morning.