LoL, it's digital Mercantilism. They will pay a fee (read: tariff), and they will get favored content (read: customer protection). This is epic fail actually. Especially since the content is stripped down anyway and only offers the same modes on the same maps for an extended period of time. Anyone who buys into this is kinda retarded. So maybe they will get rid of the map packs for sale thing, but this will make customers pay more for the good in the long run.
Look at it this way: Black Ops has been out for 8 months now. There are two map packs in that time. That means that if they were to do something similar to what they seem to be describing (though the details are completely sketchy, so it's all speculation at this time), how could the charge a monthly fee of $8 under the current release schedule and have customers not be paying more than they are now for just buying separate map packs. That would make a map pack $32 ($8*4 months). Or, would they be releasing like a map a month... which works out to the same kind of cost to schedule ratio.
They would have to significantly turn up software output for it to be worth while. Also, as one poster pointed out, they are going to strip the free one down. It won't even track your stats anymore? That is asinine. I gotta say, I do see Battlefield 3 picking up in popularity at this news, at least on the PC.
They will surely sell a whole lot of copies of MW3, and initially the service will probably do pretty decent. But after a couple of months, I think you would see a lot fewer people willing to pay for more of the same stuff from month to month. Then, keeping the pay service going, between running servers, stat updating, and that combined with less income to that end of the service, it will most likely become a liability. But, they have more money than god at this time. So, as bad business goes, they will lose on one end as long as the other end is doing well. It's still just bad business.