This is hard to say. I know lots of designers and web developers (and also myself) who think this is a douchebag thing of apple to do. That said most people I've spoken about it just laugh and don't care. Real/serious developers are not fanboys, and it goes both way. Not Apple fanboys and not Adobe fanboys. Want a site designed sure...want a real rich media experience great a flash site it is, want something in the iPad because it's the cool thing now? sure HTML5 it is. This is not necessarily a bad thing for real developers. This won't kill flash for now. I think HTML5 is the next thing, the NEXT thing, when it can do half as much as flash can.
Html coders are a dime a dozen, good one more scarce. Good object oriented coders (Flash), are scarce, but they usually have a very good understanding of coding/scripting and Html is also easily doable for them too.
This causes problem only with bad Flash Developers that all they can do is Flash.
No biggie, Apple can do what they want. They just follow the money. And so do good developers.