Microsoft is expected to launch Version 8.1 of its Windows Phone platform on day one of its annual Build 2014 developers' conference in San Francisco that begins April 2.

Pundits, however, said it's unclear whether Version 8.1 or other Microsoft moves later this year will have much of an effect on Windows Phone's market standing since the platform is well behind Android and iOS in terms of mobile apps for users.

The global market share of Windows Phone is just under 4%. This share hasn't improved much since the first version, Windows Phone 7, was launched in October 2010.

Analysts said an important rumored new feature of Version 8.1 is Cortana, the code name for Microsoft's new voice-activated digital assistant, which compares to Google Now and Apple's Siri.

A Windows Phone 8.1 Preview for Developers could be announced at Build 2014 but won't be released until April 10, said WPCentral.com. A few developers have already seen the 8.1 preview, some since February.

Microsoft is expected to announce Windows Phone 8.1 Wednesday. Later in the day, Nokia is likely to launch the Lumia 630 and Lumia 930 smartphones both running Windows Phone 8.1 at a separate event but also in San Francisco.

Microsoft is still on track to finalize its purchase of Nokia's handset division for $7.2 billion by the end of April, a deal that some analysts view with skepticism.

Online rumors say that Nokia could also unveil a smartphone code-named Goldfinger that will have no physical buttons and would use sensors to detect gestures. Gestures are already used in a limited fashion in some Android smartphones, but the technology's performance so far has been inconsistent.