Previous analyst predictions were right: it looks like ongoing sales of the annual Call of Duty franchise are beginning to slow down.Life-to-date sales of 2011's entry Modern Warfare 3 are behind where 2010's Black Ops was at this time last year, despite the former having a stronger debut While exact sales numbers are not public, analysts at Macquarie Equities say that Modern Warfare 3 volume sales are behind by around 4.2 percent.Notably, March sales in particular were damning, with last month's sales of Modern Warfare 3 reportedly less than half the amount that Black Ops sold at that time last year.Analysts at PiperJaffray say that these numbers could indicate significant changes in the market: specifically, the firm believes that casual players -- those who don't necessarily purchase a game at launch -- are buying less games at retail, and are instead using their consoles primarily for video streaming and other forms of media consumption.Webush Securities analyst Michael Pachter added that March's weak performance could indicate that software sales are becoming more reliant on new releases, meaning consumers are less often buying games after their initial debut.Publisher Activision Blizzard does not rely entirely on boxed retail sales for Call of Duty revenue. In fact, 34 percent of the company's revenue in its last fiscal quarter came from digital sales, much of that from the 1.5 million annual premium subscribers to its Call of Duty Elite service.