Soundwave ultimately shows up in “Revenge of the Fallen,” the “Transformers” sequel and the last one penned by Orci and Kurtzman. In this film, Soundwave (voiced again by Welker) transforms into a satellite, remaining in Earth’s orbit and monitoring communications. For the first chunk of the film, he puppeteers the revival of Megatron. His connection to Ravage is also reinvented; the panther Decepticon transforms into a missile that Soundwave can fire through the atmosphere onto Earth’s surface.
In the third film, “Dark of the Moon,” Soundwave has come to Earth and now transforms into a shiny new Mercedes-Benz. In keeping with his spymaster role, he poses as the new car owned by Sam’s girlfriend Carly (Rosie Huntington-Whiteley) and has Laserbeak (Keith Szarabajka) act as his assassin. He meets an abrupt end in the third act, but the prequel/reboot “Bumblebee” brings him back and renders him identically to his classic self. Despite the cassette-player styling of Soundwave’s appearance, the film dodges the size-shifting question by never showing him transforming.
The 2010 cartoon “Transformers: Prime” (developed in part by Orci and Kurtzman) features, for my money, the best modern update on Soundwave. He transformed into a Predator drone plane and thus his robot mode wasn’t boxy, but slim and sharp (the drone’s wings formed his arms, see here). His face was also a blank viewscreen, taking his classic visor to the next extreme. “Prime” Soundwave wasn’t just taciturn, but completely silent; when he did choose to verbally communicate, it was via recordings of other characters (more than once, Soundwave literally threw Starscream’s words in his face). This also makes Soundwave even scarier; the implication is that he’s always listening.
Had Orci and Kurtzman come upon the idea earlier, I think “Prime” Soundwave could’ve been the perfect template to bring the character into live-action.