Elon Musk is developing a new "top secret Tesla masterplan." Let the speculation begin.

Shares of Tesla Motors (TSLA - Get Report) traded up nearly 4% on Monday following a Musk tweet Sunday that he was working on an update to his 2006 manifesto that laid out the ambitious path that Tesla has followed. The tweet follows a stretch where the automaker has been buffeted by bad news, including a fatal crash by a driver using its autopilot technology, questions about disclosure stemming from that crash, and Tesla's holiday weekend release stating that it had failed to meet second-quarter delivery goals.

Working on Top Secret Tesla Masterplan, Part 2. Hoping to publish later this week.

— Elon Musk (@elonmusk) July 10, 2016

The idea of a master plan is sure to thrill long-time Tesla advocates, as it calls to mind the grand vision of a greener future that Tesla has spent the last decade pursuing. It has also led to a round of speculation as to what the CEO might have in mind this time around.

Some in the auto industry have been predicting that Tesla will soon formally throw its hat into the ride-hailing business, and Musk could use the new plan to outline a plan to compete against the likes of Uber Technologies and Lyft eventually using autonomous vehicles. There is also a chance that the company could formalize its development plan for future vehicles, with an SUV derivative of its upcoming lower-cost Model 3 and a potential truck the subject of past rumors.

But for all the excitement it is quite possible Musk is simply hoping to use the hype that is sure to surround a new master plan to try again to persuade markets about the wisdom of his proposed deal $2.8 billion deal for SolarCity (SCTY) . Last month, Tesla went public with the idea of buying SolarCity, an installer of residential and commercial solar panels that like Tesla counts Musk as a major shareholder.

The bid was subject to due diligence and a definitive offer, and the two companies could be nearing completion of negotiations and ready to announce the formal agreement.

Musk, in an investor call at the time the deal was first proposed, said. "I have zero doubt about this," but the initial negative reaction by Tesla shareholders -- the company lost more in market capitalization than the value it offered for SolarCity -- and a steady stream of commentary from both major investors and journalists in the weeks since indicated the markets are far from convinced.

Tesla and Musk see the deal as creating "the world's only vertically integrated energy company," able to sell a green-focused company with the means to generate clean energy, Tesla batteries to store it, and a vehicle to use it. Musk has been an optimist on energy generation and storage even as SolarCity has failed to turn a profit, saying in May at Tesla's annual meeting that the company's home battery business has the potential to one day exceed demand for electric cars.

But many investors are more focused on SolarCity's fragile balance sheet, coupled with Tesla's already ambitious production schedule and future capital requirements, and worry the company is biting off more than it will be able to chew.

Musk's original master plan telegraphed the concept of buying SolarCity, stating that Tesla in addition to using initial sales to build scale and fund more affordable vehicles the company would also "provide zero emission electric power generation options" in the future.

If there is a deal announcement on the horizon, the time has come to reassure investors and talk about what the next 10 years might have in store. It will be interesting to see what Musk has in mind.