I think every element can has futuristic cards, though cards like Armagio, Graviton Mercenary, Acceleration, Photon, Maxwell's Deamon, Singularity, Nova, Mutation, Schrodinger's Cat, Black Hole etc. are already enough futuristic-like. However, here are a few ideas of mine:
: Shock Trooper (a human in futuristic uniform who attacks with electricity, probably dealing 'spell' damage)
: Helicopter (a high-tech helicopter with a CC ability or ability to 'transport' troops, like the Graviton Transport idea from the Forge)
: Stealth Plane (like real-life Stealth airplane in appearance with cloack passive ability or something like that)
: Necromaton (a dead body which still 'lives' via machinery and high-tech equipment, probably it would look like Stroggs from Quake series)
: Demolition Man (a high-tech explosives expert who can destroy permanents via explosives)
Mad Scientist (a scientist with a special mutation active ability, which always turns the target to an Abomination|Micro Abomination)
Flamethrower (a weapon which deals little damage but it has a CC or a mass-CC ability)
Mecha (very powerful and expensive robot with momentum)
Alien Plant (a carnivorous alien plant with devour ability)
Laser Beam (a 'spell' which deals damage according to how many Photons you have)
Desert Tank (a futuristic tank which has a repair active ability that dealys it for 1 turn but heals it up to 5 hp)
Submarine (a futuristic submarine which gains +3|+0 in a flooded area)
Marine (a futuristic soldier who can serve any element)