Many modern online games go to great lengths to try to prevent players from cheating - some of them quite invasive. I hope that in the future our computer systems are architected to make it trivial to subvert such malware, but where does that leave players of on-line games who want to avoid playing against cheaters?
Well, I hope that in the future, online games are designed in such a way that cheating is impossible - that is, no information sent to a player's computer that would allow them to gain an unfair advantage and no information received from a player's computer is trusted to be untampered-with. In such a game, a player would be allowed to use whatever client software they like, and would be encouraged to use client software that gives them the best odds. Serious golf players pick the clubs that give them the best advantage, tennis players pick the best tennis rackets and so on - why should on-line gaming be any different?
One implication of this is that the best games will be Turing tests of a sort - a game of aiming accurately and reacting quickly won't be much of a challenge since the computer can do those things better than human players. Tasks that humans can do well but computers are poor at will need to be integral to the game.
That's not to say that games of aiming accurately and reacting quickly won't exist, but if they are played online they will be played between people who each other and trust each other not to cheat, not between strangers.