Tesla originally planned to unveil a new product on Monday, but those plans have changed, as the product apparently isn't quite ready.
"Moving the Tesla announcement to Wednesday," Tesla CEO Elon Musk wrote in a tweet on Sunday. "Needs a few more days of refinement."
What refinement, or even for what product, is unclear. Musk previously tweeted the product is "unexpected by most".
Some have speculated Tesla plans to announce Autopilot 2.0, the next generation of its semi-autonomous driving feature on the Model S, Model X, and perhaps Model 3.
Tesla and SolarCity shareholders don't vote on the proposed $2.6 billion merger until October 27. However, Musk could go against some investors' wishes and announce a product with SolarCity before gaining shareholder approval.
Update 10/19: Tesla CEO Elon Musk said on Wednesday the announcement will be "Model 3 part 2" and will come at 8PM EST. Musk has previously hinted semi-autonomous driving for the Model 3 , along with other premium features ZDNet will keep you updated on the latest.