After a tough few weeks for Tesla, Elon Musk says he has something big up his sleeve. 

At least, that's one interpretation of a tweet Musk sent out Sunday night: 

The tweet could be a response to criticism the company's co-founder and CEO has recently faced. In late June, Tesla offered to buy SolarCity, the solar-energy company co-founded by Musk and currently led by Musk's cousin, Lyndon Rive. Tesla's stock fell by 10 percent following the announcement, and analysts widely panned the potential deal, calling it a "conflict of interest" and "a brazen Tesla bailout of SolarCity." The latter company is currently not profitable and its stock dropped by 15 percent in 2016's first quarter.

Then news hit that the National Highway Traffic Safety Administration was investigating a death that occurred in Florida while the driver had Tesla's autopilot feature activated. Musk had not revealed the crash, which occurred May 7, to shareholders before a public offering of $2 billion in shares nine days later. Musk responded by telling Fortune that the crash was "not material to the value of Tesla."

It's hard to know exactly what Musk's secret plan could be. The "Part 2" refers to the fact that Musk initially wrote about Tesla's master plan in 2006. The blueprint at that time entailed building a sports car, then continually reinvesting the cash from those models to build more affordable versions. The first of those affordable versions is coming soon: The $35,000 Model 3 is due to be released late next year.

One guess is that the upcoming announcement might have something to do with the autopilot feature that's recently come under fire. Another, non-fatal Tesla crash occurred in Pennsylvania on July 1. The driver told authorities that the car had been on autopilot when the accident happened, though that detail is yet to be confirmed by Tesla or those investigating the crash.

In a blog post earlier this month, Musk called the fatal Florida crash a statistical inevitability and pointed out that autopilot driving is still safer, statistically, than manual driving. Musk also stressed that the feature isn't meant to fully replace manual driving, but to serve as a form of assistance to the driver.

Whatever Musk's big reveal is, lots of eyes will be watching. Teasing it like this means there will now be even more pressure on him--and on Tesla--for it to be a good one.