That is correct. Your 2006 week was banked with RCI, meaning that you can use it for an RCI exchange. Your 2006 week is not otherwise available to you. However, you cannot exchange through RCI unless you have an account there. Contact RCI, open an account and you can get the banked week deposited into your account so that you can request an exchange. The sooner you do it the more likely it will be that you'll get an exchange you request.
As for II, you cannot deposit a week from your resort with II unless your resort is affiliated with II. Most resorts have an affiliation with only one of the two major exchange companies. I'm not positive, but I believe Stonegate's affiliation is only with RCI.
Even if your resort is affiliated only with RCI, you can choose to reserve your future weeks (starting with 2007) and exchange either through RCI or one of the independent exchange companies that are discussed on this forum and in the TUG Advice section (link at the top of the page).