Egyptian Desert Subtheme
The Adventurers
in the Future
Amazon Jungle Subtheme
Dinosaurs
Dino Island Subtheme Orient Expedition Subtheme
Indiana Jones Theme

Adventurers 
In the Past
The Future
Here is a list with some theories about the future of the Adventurers theme. From China why doesn't Johnny head south through Indochina, Indonesia and maybe even the Philippines and end up home in Australia? You are very welcome to present your own ideas or comment these.

Southeast Asian Subtheme
I think it could bring some nice animals: tigers, more elephants and others.
Pros: Following the tracks of Indiana Jones, Johnny Thunder still needs to go to Asia, maybe to Angkor Vat.
Cons: No major change from the Amazon: overgrown temples in the jungle.

Australian Subtheme
Pros: Johnny longs to get home. 
Cons: What needs to be explored? No ancient buildings but maybe a treasure?
Aborigines, Kangaroos and Koalas could be included.
Arctic/Antarctic/Greenland Subtheme
I think this would bring us igloos, kayaks, dog-sleds and white vehicles (maybe a snow sleigh?) surrounded by white BURPS, an big expedition ship would be nice though. There will probably only be one Inuit though.
Pros: The Adventurers exhibition area in Carlsbad consists of three sub areas: a desert, a jungle and an arctic/antarctic. 
Cons: Too close to the Arctic Subtheme from City/Town. All of the minifigs will need a new torso and headdress to withstand the immense cold weather. No buildings or big treasures to be found at the poles only the glory to get there first. That would be enough to bring Johnny Thunder there but what about Mr. Hates and Slyboots?
African Safari Subtheme
I think it would be cool to have lions, more elephants and other wild animals. This could also be Madagascar.
Pros: The Adventurers goes looking for King Salomon's mines just like Alain Quatermain.
Cons: The Adventurers has already been to Egypt. What skin color will the African minifigs have?
Mesopotamia/Arabia Subtheme proposed by Ramona Schuster
Pros: Would fit in quite well with the rest. There is much action and excitement hidden in the sands of the Arabian desert, like Aladdin type stuff: fantastic tombs that contain the fabulous treasures of lost sultans. And there are cool buildings, like palaces and temples.
Cons: Maybe it is too close to the Egyptian Desert Subtheme and the new Indian Subtheme, and the buildings might be a little too fancy. 
Roman/Greek Subtheme proposed by Michel Lalande, Mark Lindsey and Jeroen Willemse
There could be a labyrint with the Minotaurus, Mr. Hates will go to the underworld and join forces with Hades and meet Cerberos (Fluffy ?). There could be a treasure on the Olympus, perhaps a temple of Aphrodite, where Kilroy gets in some kind of a trance. Perhaps Johnny discovers a statue of gold...
Pros: Would fit in quite well with the rest 
Cons: Maybe it is too close to the original Egyptian Desert Subtheme

European Museum/Zoo Subtheme
Adventurer museum and zoo sets might be made where there are empty spots to put all of their findings.  Also, dinosaur skeletons could be made. I think it would be very cool to have a lego museum.

Atlantis/Coral Reef Diving Subtheme proposed by Mark Lindsey, Randy Swan and Elizabeth Jennison
The Adventurers could go looking for a Spanish Galleon, an airplane lost in the Bermuda triangle or maybe even Atlantis. It would be cool with those old time diving suits and big helmets. Perhaps we could see the inclusion of lego mermen and mermaids. Upper torso that of a lego man and the bottom a new jointed fish tail. Think of all the cool shell shaped new pieces we'd see in the sunken ruins. As well as the super technology of the Atlantians. Strange organic looking shaped vehicles that everyone is trying to be the first to retrieve. The sets would include squids and sharks, as well as the remains of the ancient Atlantians. They would have to wear new looking crowns and weird strange weapons. Also giant sea horse are a must have. Diving helmets would be a must for our characters, with a string or tube on them for air. A boat for the go guys with a sea captain on it would be great. A friendly dolphin. We could get a Harry Cane with knit ski cap on like Custo wore. Mr. Hates would need some new thugs including a captain sort of like the one from the film Jaws. Atlantis play sets would include the Treasure of Atlantis. This would be the big set.  It would come with a small boat, temple that is under the sea, with a merman, three skeletons of atlantis, animals and the like. It would also have Johnny thunder in diving suit. The set would be fraught with traps, such as a cage that would trap you under water, and a stature with eyes that are really spears and can fall out. The treasures of the set would include some weapons of ancient origin, and perils. That is the big treasure for the treasury set. There will be three giant clam shells.  One contains the giant pearl of Atlantis. The other two hold magnets, and the way it is rigged is that if the shell is opened then the character is pulled in. Other sets would include The Throne Room, and an underwater observatory, with a huge telescope that uses a diamond as a lens. It is of course bobby trapped. There would be a sea plane, and a good guy boat and one for the baddies.
Pros: This would be very different subtheme
Cons: Maybe it is too different. Johnny and his mates can't breath underwater. How much air is going to be in those air tanks?

Pirate proposed by Rebeca Ginart
The Adventurers will try to find Captain Redbeard's treasure in a parrot's cave. They travel across the world for clues on maps. They spot a broken-down Black Seas Barracuda and a clue that means they will have to fight old pirate skeletons. Even a group of surviving tricorner pirates will block there paths. Will they pass them, or will they discover something that will pass them automatically? Only the understanding of clues can tell.

U.F.O. proposed by Richard Day
This one would involve U.F.O's having landed in the United States Mid-west in the time of the Mazasai Indians some thousands of years ago. Johnny thunder and gang would have to excavate the remains. In Johnny's way would stand Mr. Hates, Alien Lego men, and Native American Lego men.
Pros: Johnny Thunder hasn't been to America. 
Cons: This would really be something different.

Canadian/Alaskan/Siberian Subtheme
Cons: Johnny has already been to Himalaya.

Disease Subtheme proposed by Elizabeth Jennison
Pros: Even Adventurers get sick from time to time
Cons: Diseases takes a lot of work. And it may pass on to the other characters until they're all sick and tired. But it can add drama. Trying to succeed dispite a great drawback.
The Adventurers will go to MOCland
Pros: Most themes lately has had a three year life cycle with only two subthemes. 
Cons: There is no rule without an exception. 
I hope this is not the immediate future.