What makes today's release even more intriguing is that the game vanished from Steam on the eve of the new content's launch. There has been a bit of tension between Steam and EA since the launch of EA's new Origin platform, which has limited digital exclusivity of some EA published games such as Star Wars: The Old Republic to the new digital service. While no solid reason has been given for the game's sudden disappearance, RPG notes that Steam has recently changed its terms and conditions, which puts companies that sell content through any medium or service other than the Steam Store in violation of their agreement with Steam. This has also led to the removal of another EA published game last month with Crysis 2.
Given that Dragon Age II uses an in-game store, one could speculate that this may be behind its sudden disappearance. But RPG so aptly points out, nothing is confirmed as of yet and anything at this point is purely speculation.
The positive side is that according to BioWare's Luke Barrett, if you did purchase the game through Steam it should still be supported for play. Beyond that he only acknowledged the issue but offered no further details about the game's removal.