Does anyone really think all 100,000 of those downloads are by software developers? I'd bet that 90% of the downloads were done by clueless end-uses who have no need for, or ability to use an SDK. If I'm right that means 10,000 developers did download the SDK. Even that is a huge number. Maybe it's 98% not 90% 2,000 real developers seems about right
Even if you were right (and your numbers are just guesses and very low ones at that), what is exciting for many young unaffiliated programmers (of which I am not one) it to start writing apps. Some might get lucky and write an app that will really catch on. This is a very democratic process (even with the limitations that Apple imposed).