Microsoft (MSFT) stock closed at an all-time high on Monday as the ouster of Sam Altman at OpenAI sent shockwaves through the tech world over the weekend, surprising everyone from Microsoft CEO Satya Nadella to investors on Wall Street and VCs in Silicon Valley.

After a weekend-long back-and-forth, Altman is no longer with OpenAI. Instead, he and fellow OpenAI co-founder Greg Brockman have joined Microsoft to lead a new advanced AI research team, per Nadella.

But on Monday afternoon, the Verge reported that Altman's deal with Microsoft is not official.

RBC Capital Markets managing director Rishi Jaluria described the past few days as the "most eventful" in his more than a decade covering software. Jaluria categorized the end result as a "huge coup for Microsoft," as he still sees the tech giant as the leader in generative AI.

"The worries I think everyone had were the pace of innovation would slow down, some of the AI halo around Microsoft that it's been enjoying in its [stock] multiple would start to dissipate," Jaluria told Yahoo Finance Live. "Customers would get worried. I think by bringing in Sam and Greg, and Sam is really the ultimate visionary when it comes to AI, it's really the best-case scenario for Microsoft."

Microsoft shares closed at $377.44 on Monday, up more than 2%, after initially falling on Friday afternoon following the announcement Altman was out at OpenAI. Meanwhile, Alphabet (GOOGL) shares gained about 0.7% during Monday's trading session.

For investors, there are still concerns about how uncertainty at OpenAI could impact Microsoft's business in the short term. Nadella mentioned on the company's most recent earnings call that Microsoft's Azure cloud services were being used by OpenAI.

Evercore ISI analyst Kirk Materne noted that any fundamental risk to Microsoft is largely "contained" with Altman now onboard.

"When taking a long-term view, hiring Altman and team might end up being a better outcome vs the prior status quo," Materne said. "Clearly, there is still some risk to Azure if OpenAI growth were to materially slow, but we think the long-term opportunity around GenAI for Microsoft trumps any near-term risk associated with the OpenAI disruption."

Oppenheimer analysts Timothy Horan and Edward Yang wrote in a research note Monday that this is a "win/win" for Microsoft.

In his own note to clients, Wedbush analyst Dan Ives suggested Altman could've ended up at another competitor, writing, "Instead he is safely in Microsoft's HQ now leading the company key AI efforts which we expect many key scientists and developers to leave OpenAI and head directly to Microsoft."

Microsoft, which invested $10 billion in OpenAI in January, still plans to continue working with the disruptive technology behind the popular ChatGPT, according to a tweet from Nadella.

But the aftershocks are still being felt at OpenAI. Early Monday, more than 500 OpenAI employees signed a letter urging the board to resign — or else these employees would leave themselves.

"We, the undersigned, may choose to resign from OpenAI and join the newly announced Microsoft subsidiary run by Sam Altman and Greg Brockman," the group of employees wrote in a part. "Microsoft has assured us that there are positions for all OpenAI employees at this new subsidiary should we choose to join. We will take this step imminently, unless all current board members resign."

The letter is one example of the strategic advantage some on the Street believe Microsoft just gained against competitors by adding Altman and Brockman.

"Hiring qualified generative AI data scientists, engineers, and talent is very, very, very, very difficult," Jaluria said. "Microsoft is now a destination employer for generative AI engineers. OpenAI was that. I think this maybe even increases the gap between Microsoft and others that are trying to compete."

Fred Havemeyer, an analyst at Macquarie, wrote in a research note on Monday this new team at Microsoft will be able to "hit the ground running."

"We believe Microsoft has both preserved its AI product roadmap and assembled formidable competition for generative AI startups and Google DeepMind," Havemeyer said.

Josh Schafer is a reporter for Yahoo Finance.

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