To me each and every chapter looks like it could be the end, but a manga is only 19 pages a week, and as all manga-ka do, they drag it on to keep us in suspense, so Enies Lobby does most likely have a few chapters to go.
I think Vivi's just there because people miss her, and Oda-sama is trying to bring the feel that even though their arc is done, these characters were lovable and other mushy stuff…like the character shouldn't be forgotten, even like the BW guys and their cover arcs a while back.
It's a good feeling, like after all the Enies Lobby stuff, I'm sure the CP9 and Water 7 have left a huge impression in One Piece history and I know I'll miss them (..more so I'll miss Kaku and Paulie), but we'll get to see them from time to time
I'm just rambling now eh? :S