MB confirmed Ener-G-Force is sci-fi. G to continue to 2020+. 
Mercedes-Benz unveiled a flight of fancy called Ener-G-Force, a view of what a rugged SUV could look like in 2025. "Pure science fiction," cautioned M-B spokesman Christian Bokich. That is, it's not a teaser of something in the pipeline, which many auto show "concept" cars are.
As a replacement for the big, blocky M-B Gländewagen (a.k.a. G-wagen or G-class), it would have to wait a long time. The G-wagen is in the plans at least through 2020.
http://www.usatoday.com/story/money/cars/2012/11/29/mercedes-suv-fancy-hydrogen-fuel-cell/1733411/
http://www.mbusa.com/mercedes/benz/innovation/future/model-Ener_G_Force_Concept

Mercedes-Benz unveiled a flight of fancy called Ener-G-Force, a view of what a rugged SUV could look like in 2025. "Pure science fiction," cautioned M-B spokesman Christian Bokich. That is, it's not a teaser of something in the pipeline, which many auto show "concept" cars are.
As a replacement for the big, blocky M-B Gländewagen (a.k.a. G-wagen or G-class), it would have to wait a long time. The G-wagen is in the plans at least through 2020.
http://www.usatoday.com/story/money/cars/2012/11/29/mercedes-suv-fancy-hydrogen-fuel-cell/1733411/
http://www.mbusa.com/mercedes/benz/innovation/future/model-Ener_G_Force_Concept