Very nice! I like the idea of Soundwave as incredibly loyal. The scene in the movie "As you command, Megatron" where he picks up his fallen commander and runs for his bloody life while under fire really nails my take on Soundwave. Of course, as others mentioned, there are many interpretations of Soundwave...
With the message on the disk safely encrypted, Soundwave kills himself. If the plan works and history is rewritten he'll wake up in 1984 in a different timeline with Prime already dead. It goes around in a circle slightly, but this was the way Time Travel was explained in Beast Wars.
He kills himself so as to spare himself the indignity of living on a Cybertron where the Autobots win the Great War. And with Megatron already dead and the Decepticons all but a spent force, he'd rather be dead too.
The Time Storm seen in BW wasn't a splintering of Time and the creation of a new, alternate universe, it was a massive rewriting of history - the same history in the same Universe. The BW characters would have disappeared as soon as Prime died, as they were beginning to when phasing in and out of existence.
Soundwave has no reason to continue to exist in that reality. The Decepticons are finished, the Autobots are going to win, and he'll be hunted down for his part in the war. He's much better off to end it on his own terms, with the plan in place to rewrite history (and him killing himself) sometime in the future.