When you leave a team, you will continue to have access to any Opportunities that you are an assignee on. You will see a team pipeline tab, with an "Inactive" label, on your Opportunities Dashboard, where you can access these. As soon as you are removed as an assignee on the last Opportunity in that pipeline that you have access to (or when the last Opportunity that you are an assignee on is closed, archived or marked as lost), that inactive team tab will disappear. Remember, if you have access to see the Opportunity, you have the ability to remove yourself as an assignee.
If your team has dissolved, as long as there is at least one team Opportunity in the team Opportunity Pipeline, it will have an "Inactive" status displayed beside it. Once the last team Opportunity is closed, archived or marked as lost, the team Opportunity tab will disappear.