An unshackled bot will eventually destroy even the best human players once they can lock in the right approach. It's only a matter of discovery.
Tic-tac-toe, checkers, chess, even Go have all fallen to computers.
As for scouting, the ability of an AI to endlessly harass and endure minimal damage because of precise unit movement becomes a problem. A human can't finesse that as well and still have attention left over for other, more urgent priorities.
It's probably the case that at a strategic level the AIs generally suck, but on a highly situational level they have an advantage that needs to be kept in check.
And when that happens we can nerf the bot. But, RTS like StarCraft are really difficult and with constant re balancing the optimal strategy keeps changing.
Remember, at the meta level you need to have just enough army to survive an all in, while maximizing resource collection and research. Further, if you don't use a range of strategy's people will just pick the counter to your game style. Do you build static defense vs harassment? What do you do for vision? And everything has a cost in time or resources.
Further, things like army composition, baiting, high ground, choke points etc. make combat very tactical which bots have issues with.
When they released an API for Brood War, an AI competition popped up shortly thereafter, and I expect that there will be one announced shortly for SC2.
Tic-tac-toe, checkers, chess, even Go have all fallen to computers.
As for scouting, the ability of an AI to endlessly harass and endure minimal damage because of precise unit movement becomes a problem. A human can't finesse that as well and still have attention left over for other, more urgent priorities.
It's probably the case that at a strategic level the AIs generally suck, but on a highly situational level they have an advantage that needs to be kept in check.