It's going to be hacked. Look at every CoD since CoD4. Hacked on all systems. But they will most likely ban like treyarch did with black ops. BF3 won't be hacked though, DICE isn't retarded.
I'm going to play legit, but I will probably be playing BF3 a lot more than MW3... I already know MW3 will be worse than MW2 was in the long run, look at their killstreak system it's going to be killstreak fest non stop, and everyone will be invisible with annoying perk combinations. You can build up killstreaks by getting kills, objectives, AND assists... It's going to be ridiculous. And not only that, but killstreaks stack, and chain. So even the WORST kids EVER will be able to get any killstreak they want. And Objectives and Kills both only add 1 point to the killstreaks, so the Objective part is just a waste, they should have added 20 points on to all of the killstreaks.
MW3 competetive will be good, like MW2's was, but pubs are going to be a joke. BF3 is going to be the game for me. Battlefeild is so much more intense.