No, fuck no, god dammit, and suck my dick. Modern Warfare 2 ended on a cliffhanger, I don't want to see what this dick head Riley did before the series began, I want to see Soap and Price's story conclude. Wasn't that why the comic was released in the first place? To tell us who the fuck is this Ghost character and why we should care about him?
Example: Halo (Story begins) Halo 2 (Story hits its climax) Halo 3 (Story ends) Halo: Reach (Prequel). THAT is how you do it.
Example 2: Devil May Cry (Begins) Devil May Cry 2 (Ends) DMC 3 (Prequel) DMC 4 (Interquel). Another example.
How NOT to do it: Call of Duty 4 (Begins) Modern Warfare 2 (Continues) Modern Warfare 0 (What the fuck?)
No. You don't leave your audience in the dark. For any reason. That's not how it works. Period. The end. Fuck you. End your series proper THEN release your prequel... Perhaps as DLC to "MW3". Also do us a favor and put out a multiplayer beta. So we can fuck it up. And then in your final game, we can't fuck it up. Perhaps add some variety to the gameplay much like CoD 4 and Black Ops (Granted Blops wasn't all that stealthy, but it had a nice tinge of variety.)