There are no final 3 episodes. They were never filmed. The show airing on BBC this Sunday is a compilation with 2 of the films that were made for those episodes. After this final episode, Top Gear is done. Dead. Finished. Well, the real Top Gear anyway.
I'm assuming the old description for this episode is no longer what's going to air. But I was curious as to which segments were filmed that we have yet to see...does it look like some might not see the light of day?