Adobe announced the planned launch of Adobe Media Player later this year. This new player offers multi-format playback, along with the ability to deliver paid for content. It will also enable the playback of high quality flash-based content, and certainly sounds (on paper) to be a strong challenger.
Quote: "Adobe Media Player is developed using Apollo, the code name of Adobe’s recently announced application runtime that empowers content publishers and web developers to build and deploy rich Internet applications (RIAs) on the desktop using technologies such as Flash, PDF, and HTML. Adobe Media Player is planned to be available as a free beta download from the Adobe Web site later in 2007 with full availability expected by the end of the year, from Adobe and a wide range of media and technology partners."
You can check out the full press release here.