From what I've read about what they've said about their plans, Clarkson, Hammond and May intended to wind things down, giving some closure to what they've spent the last 12 years doing, and letting Top Gear Mk.2 ride... drive off into the sunset. The guys wanted to leave things so that anyone making a go at Top Gear Mk.3 could start fresh. Because, frankly, the the Mk.2 version has gotten stale and they know it.

What's really going to happen? I don't know. We'll see.