Feature set over here claims that:
Enable the development of apps that use very large bitmaps. BitmapData objects are no longer limited to a maximum resolution of 16 megapixels (16,777,215 pixels), and maximum bitmap width/height is no longer limited to 8,191 pixels.
Does this mean that limit does not exist anymore, or it just has been raised to a greater value (as it used to be in previous versions)?
It's just limited by RAM you have (available for FlashPlayer).