While you're right about KSC, Disney may have counted on the average tourist not knowing all it has to offer. Same goes for Living Seas vs. Sea World. Given that MGM was an obvious shot at Universal, AK was an obvious shot at Busch Gardents, and PI was an obvious shot at Church St. Station, I'm inclined to believe the powers that be thought that Mission: Space and Living Seas would keep at least a few guests on property.
While IOA seems the most obvious current threat to WDW in Orlando, I've seen other posts that suggest it's just not that popular--not even as many visitors as AK. Does anyone have hard numbers?