With Adobe's acquirement of Macromedia a new strong alliance against Microsoft has formed in the browser application market:
"What's taking shape is the ultimate battle for the browser," said Paul Colton, CEO of Xamlon, a company that provides tools for creating applications that run in Microsoft's .Net framework. The company this month added the capability of letting its developers output Flash movies. "This [merger] play is about gaining dominance in the browser applications market," Colton said. "The reach of PDF and Flash already go a long way, and the combination of those two will be very intense."
More info about the prospects of the Adobe-Macromedia alliance can be read at Silicon.com