Just seen the new full trailer, and (major geek alert!) caught a glimpse of a kind of rocket sled in it, which is also a sequence in an earlier draft of Indy 4 called; Indiana Jones and the Saucermen from Mars (awful title, but very good script). Anyway, for anyone who's interested below is an extract of the script for that sequence. In it the character of Veska is a Russian spy sent to retrieve an alien artifact, and this happens somewhere in the desert of New Mexico (Area 51?)...
INT. BUNKER - DAY
The four rockets ignite with a DEAFENING ROAR, filling the concrete bunker with intense exhaust that blasts out the chimney top.
EXT. BUNKER - DAY
The rocket sled catapults from the bunker at 100 miles an hour down the five-mile track. Indy and Veska cling to the metal chassis. Indy’s face ripples from the G-forces. His grip begins to slip. He strains for a better hold.
Veska, in a sheltered indention of the metal skeleton, sees Indy’s grip slipping and tries to kick him off. His boot grinds Indy’s fingers against the metal. Indy grimaces but holds on. Veska tries again. Indy slips back toward the flaming rockets before regaining a hold.
Veska sees how close Indy is to the burners and tries one more time to knock him loose. But this time Indy is ready. Just as Veska raises his boot Indy yanks a rubber hose from the engine and sprays hot oil over the spy.
Screaming in pain, Veska looses his grip. His body whips past Indy through the flaming burners which ignite the oil and toast him instantly. Veska’s crisped remains are left behind the speeding rocket.
Indy’s own grip is slipping. He sees a conduit marked “OXYGEN INTAKE” and pulls the hose. The engine and the four burners immediately snuff out just as he loses his hold and flies off the back. Rolling away from the track, Indy comes to a stop and lies motionless. Slowly he raises his head. The desert is a mirage. Through the waves of heat he sees an ambulance and a car approaching before he drops exhausted.
The car and ambulance pull up next to Indy. Two men hurry out of the ambulance and rush to Indy. Indy tries to open his eyes but the men stand in the blinding sun. They speak in Russian, but one of the voices is familiar to Indy...
Not sure whether it will keep in line with that ending, but I'm pretty sure its the same sequence that appears to be in the new trailer. Sounds good to me!