It was a bold choice for Modern Warfare to remove the mini map from Call of Duty, something that was done for the opening of the beta. Infinity Ward then decided to bring the mini map back, but without its full capability, now no longer showing enemy gun fire. Rumours are currently circulating that the mini map will be fully restored in a November update.
The Mini Map Will Return In November
TheGamingRevolution is notorious for inside information and leaks within the Call of Duty franchise, he now claims that the mini map will be returning to normal by the end of November.
This should return with the game update that is due in late November. Infinity Ward have already been hard at work fixing bugs that have been found in the game. Despite the optimism around Modern Warfare, it has been met with its fair share of criticism; especially regarding the maps. There's "a big overhaul coming" he claims and changing the mini map back to normal would be a great step in the right direction for the game. The mini map makes Call of Duty what it is and with it being altered, people have been quick to express their concerns about how the gameplay has suffered as a result.
This is all simply speculation, but TGR has proven to be a very credible source for this information in the past.