At Microsoft's Professional Developers Conference (PDC) this week, the future of Silverlight is one topic that has gotten short shrift. There have been no sessions about Silverlight 5 and only one mention of Silverlight in the kick-off keynote.

But there were plenty of mentions of HTML 5 and Microsoft's commitment to that technology, not only in the next version of its Internet Explorer browser, but also as the glue "facilitating a level of independence and innovation between the back end and the front end" (as CEO Steve Ballmer said during an October 28 keynote address at the PDC).

So what's a developer to make of Microsoft's messaging (or lack thereof) about Silverlight at its premiere developer conference?

I asked Bob Muglia, the Microsoft President in charge of the company's server and tools business, that very question and got what I consider to be the clearest answer yet about how Microsoft is evolving its Silverlight strategy.

"Silverlight is our development platform for Windows Phone," he said. Silverlight also has some "sweet spots" in media and line-of-business applications, he said.

But when it comes to touting Silverlight as Microsoft's vehicle for delivering a cross-platform runtime, "our strategy has shifted," Muglia told me.

Silverlight will continue to be a cross-platform solution, working on a variety of operating system/browser platforms, going forward, he said. "But HTML is the only true cross platform solution for everything, including (Apple's) iOS platform," Muglia said.

Muglia said there definitely will be another version of Silverlight, and that it will be "very much in line," in terms of functionality and features, as Silverlight 4, which Microsoft delivered in April of this year.

Muglia didn't share any kind of timetable as to when Silverlight 5 might make its debut. He did note that the delivery pace of Silverlight is slowing. "As with anything as it matures, the (delivery) cadence changes," he said.

When Microsoft first showed off Internet Explorer 9, its most HTML 5 compliant version of IE to date, in March of this year, questions began to arise about the company's commitment to Silverlight. Officials insisted that the two would coexist and that Silverlight would be Microsoft's cross-platform development platform for mobile, Web and PC platforms for a number of years to come, as HTML 5 was far from becoming an accepted standard.

But in the past few months, Microsoft's backing of HTML 5 has gotten more aggressive. Microsoft is pushing HTML 5 as the way developers can make their Web sites look more like apps. ("HTML5 enables you to make engaging and interactive sites. With full hardware acceleration of the browser, HTML5 pages feel and run like an app or a game," said IE chief Dean Hachamovitch during the opening PDC keynote yesterday.)

I'm guessing we'll hear something about Silverlight 5 by the time of Microsoft's Mix '11 conference in the spring of 2011. Until then, where do you want it to see Silverlight go tomorrow?