A lot of people are easily distracted by these early launches and don't realize the mistakes being made.
Don't get me wrong, the Evo 4G is hot -- if I were in the US, I'd seriously consider it even if I wasn't in a 4G area. But Sprint's announcing it now is potentially a fatal decision. By the time the phone is shipping, you'll probably have seen a new iPhone -- and a lot of the hype given to the Evo 4G will have cooled off. Sprint could have an all-out marketing blitz, but unless Android has just that much more allure than the Palm Pre did, Apple could own the news again.
Not to mention that Apple probably isn't standing still. There was a leak of a taller iPhone design, so the gap in screen quality could be much smaller. And there's no doubt Apple wants a performance boost across the board.