If CA goes to a monthly subscription for a SINGLE PLAYER OFFLINE GAME, I'll just have to find some alternative to the TW series, and you can bet that fanmade versions will start popping up as the TW series starts to hemmorage customers.
I dont see why people support the whole, "Pay $50 for a game, then every four weeks pay $10 to keep playing it." system.
And, y'know, there are games FAR more buggy than MTW2 was on release. I personally dont see what people complain about. It had some gameplay bugs, but I personally have never experienced a crash or lockup with MTW2 (that wasnt caused by something else.) I had one or two crashes with RTW, but they were easy to avoid.
Also, lets not forget the people out there without A) An internet connection on their gaming computer or B) 56k. Believe it or not, they exist. Used to be me a few months ago until we FINALLY got a DSL line in our neighborhood. If CA goes to the suggested system, they'll lose a TON of customers simply because of that.

Anyway, in summary, a monthly subscription would be the death of CA.