I think Top Gear's format is great for what it is. They've got subtle changes in the new series but why change a tried-and-tested formula? What it's successfully done is brought car journalism into the homes of thousands of people who otherwise wouldn't watch it. People like my parents.
They sure as hell wouldn't sit down and watch (or enjoy) Fifth Gear, for example.
May and Hammond won't leave, it's their biggest and most successful project and they both evidently love it!