I expect music and to some extent video to stay in iTunes or similar venues. Terrified book publishers who want their DRM will likely stay in the iBooks zone, though hopefully Apple will let braver publishers in there without DRM. Customers will expect to find “books” there. It’s also clear that there will always be applications, notably games, which demand native code - Objective C on the iPad - to achieve the fastest possible response time, draw intricate graphics, or bind tightly to iPad features. There’s a future for all of those things, in their particular venues.
But for “content”, especially content that combines text with audio, video, pictures, and interactivity, web-style development has a tremendous advantage.
Arise, web developers! Our time has come to dominate!