Microsoft's server president Bob Muglia confirmed that although Silverlight was the primary development platform for Microsoft's phone platform, and that MSFT viewed Silverlight as having good prospects for some applications, the company's broader cross-platform efforts would rely on HTML5.
At MSFT's "Professional Developer Conference" there were no Silverlight sessions and few mentions, but lots of discussion of HTML5. In Microsoft's depiction of Ballmer's remarks at the PDC, for example, the word "Silverlight" appears one time (the other two times on the page aren't in the remarks, but in links outside the remarks), whereas "HTML5" appears 32 times.
Adobe's position on Flash as the standard for cross-platform development grows increasingly less credible with each defection. Shocking though it may seem, some standards even Redmond has accepted.