Now, this is a touchy subject because, no you wont get VAC banned. The Grand Theft Auto series, or any games that are not on the list above are NOT VAC secured. Be advised that I do not condone cheating in any way. So, if you do decide to use Cheat Engine on a non VAC secured game, don't come crying to me when you forgot to close it and loaded up CS:S, and joined your favorite DeathRun server or something.
I don't think MW2 will be able ban at least anyone who has already used the stat hack. It's not going to be able to tell whose hacked to a particular lvl and who has done it legitimately.
it could be possible, yes that MW2 could start monitoring your stats from that update on and ban people's accounts if they suddenly rocket up from lvl 10 to about lvl 68, but i seriously doubt that.
Really, if you used CE today, i don't think u need to be scared about being banned. If you want to be extra careful, just go up in small jumps at a time or something. CE is pretty safe, those who get banned are generally the ones who've used other hacks in the past in addition to CE.
When I ran a private server, not for CoD but anyways, I monitored anything. Distance you jump, items you buy/sell, items you trade, it would all check if did exist, but thats 'cause I didn't want hacks, scams and that kinda stuff, but I agree, I doubt they did that with CoD, why would they care? People buy it anyway.