Wall Street history was made seven weeks ago, with Elon Musk's Space Exploration Technologies (SpaceX) (SPCX +4.23%) setting a new bar for initial public offerings. As of July 25, there was 74% probability that SpaceX and Musk's other trillion-dollar company, Tesla (TSLA +0.70%), would merge before May 1, 2027. The recent surge in merger speculation between Elon Musk's trillion-dollar companies traces back to Tesla's latest quarterly conference call. When asked by Wells Fargo analyst Colin Langan if SpaceX and Tesla would one day merge, he didn't say no. Terafab is a joint-venture semiconductor manufacturing project between Tesla, SpaceX, and artificial intelligence (AI) start-up xAI.