When Microsoft kicks off its annual developers conference Wednesday, it must show it has made progress on 2015's promises, analysts said today.

"They have to demonstrate that they're building momentum from both user and developer perspectives," said Jan Dawson, chief analyst at Jackdaw Research, referring to Windows 10 and pledges the company made last year.

At 2015's Build -- Microsoft's moniker for its developers conference -- the Redmond, Wash. company set itself a goal of putting Windows 10 on a billion devices by mid-2018, and trumpeted the "universal" concept as a solution to the weak app inventory inherited from Windows 8.

Under the "Universal Windows Platform" (UWP) nameplate, Microsoft has touted a write-once, run-many model under which a single Windows app works on the unified Windows 10 framework, whether the hardware is a PC, tablet, smartphone, game console or sensor. Microsoft has expended significant resources to bolster developer tools for writing such apps, including the upgrading of Visual Studio, the creation of cross-platform toolsets to port iOS and Android apps to the Windows ecosystem, and last month, the acquisition of Xamarin.

"The No. 1 goal for Build must be to show progress with the [cross-platform development] bridges, the progress with Visual Studio in that context, and how those increment the play of Windows 10," said Patrick Moorhead, principal analyst at Moor Insights & Strategy.

Both Dawson and Moorhead expect Microsoft to illustrate progress on those fronts during the keynote that will launch Build 2016 tomorrow. The keynote has become one of Microsoft's biggest platforms for announcing its strategic path for the coming year. While not a product-laden event -- unlike, say, Apple's presentations throughout the year -- the keynote is parsed by outsiders who hope to divine the firm's efforts to convince a key audience, developers, that Microsoft's technologies can be leveraged for profit.

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Specifically, the pair agreed, Microsoft will likely herald a new number for Windows 10 adoption or usage to drive home the message that the app market is substantial for developers, and thus worth their time and investment. Dawson put his money on a number around 250 million, while Moorhead said it would be larger, close to but not yet 300 million. "The worst case would be 250 million," said Moorhead.

Microsoft last publicized a Windows 10 figure nearly three months ago, when it said that more than 200 million "monthly active devices around the world [were] running Windows 10." That number included not only PCs, but also tablets, phones and Xbox game consoles, and was not pointing to installations, but instead tallied devices that were used at least once in the prior month. Microsoft's telemetric technologies in Windows 10 let it "see" when those devices are turned on and used by customers.

The discussion of development tools, another key element of last year's Build, must also be advanced tomorrow, they said.

"Microsoft has to ensure the messages coming out of Build 2016 are ... [that it] continues to support developers beyond Windows 10, both by making it easier for them to bring existing apps to Windows and by enabling them to develop for other platforms through tools such as Azure and recently-acquired Xamarin," Dawson said in an analysis published earlier this week on Tech.pinions (subscription required).

"They'll talk about how developers can do a Windows 10 app for PCs and 2-in-1s, and then for 'free,' also a mobile app," added Moorhead, referring to the Xamarin framework. "Xamarin does exactly what Microsoft needs. Xamarin will actually crank out an iOS app in addition to a Windows app."

While that may be the result of Microsoft's iOS bridge, Moorhead said it was a "massive" difference, as the starting point for a Xamarin-dependent project is a Windows app, which is what Microsoft would prefer.

But while Microsoft will continue to emphasize that its tools let developers expand their marketable audience -- whether bringing iOS apps to Windows, or taking Windows apps to iOS as well -- the company will also keep beating its native mobile play, the analysts agreed.

"They'll make it clear that they have not given up on mobile," said Dawson of Windows. He anticipated that Microsoft would stress the business suitability of Windows-powered smartphones, if only because it's clear that few consumers have adopted the platform.

"The market has been brutal, but I think it's too late for them to eliminate mobile from the conversation," said Moorhead. Instead, Microsoft will aim the conversation further down the road by suggesting that it's well-positioned to exploit the continued move toward ever-more-powerful smartphones, and the day when smaller devices better compete with PCs on a horsepower level. Developers should take the long view, Moorhead said Microsoft will suggest.

And Microsoft will allude to the options developers have, even if Windows 10 on mobile doesn't work out. "There are different platforms, such as HoloLens, that can run these apps," Dawson said of Microsoft's virtual and augmented reality platform. "It's not just about mobile."

Nor should Windows be the sole focus of Build and its keynote. Microsoft's various cloud businesses, particularly Azure, must also get time on stage.

"Azure has always had a presence at Build, but it's grown over time," said Wes Miller, an analyst at Directions on Microsoft, who predicted significant time dedicated to how developers, especially those who concentrate on enterprise apps, can benefit from working with Azure.

Moorhead concurred. "What they need to do with the realities of running the business is talk about Azure," he said, pointing to Microsoft's position as the No. 2 player in public cloud, and in his opinion, the best when it comes to hybrid environments, where public and private cloud deployments are combined.

"They need to keep the heat on because Google is nipping at them," Moorhead said. "This is one of the biggest opportunities Microsoft has. And pragmatically, it makes sense. There are a ton of people to train and educate about Azure."

Microsoft will live-stream the two-and-a-half-hour keynote Wednesday starting at 8:30 a.m. PT (11:30 a.m. ET) from its website.