Flash support has been "just around the corner" for over 4 months. Although I think the SDK will finally put the needed pressure for apple to do something official about it. If they dont, someone else will probably write it anyway (as we have seen happen in Linux).
I hope it is easily turned off. I don't need or want advertisers burning off the millijoules of my battery with distracting ads. I've enjoyed the 1990s version of the web with static pictures for ads.
I agree though, with the SDK Apple will have to add Flash or someone else will do it poorly and waste even more power.
I think they've managed to establish a baseline expectation for how long iPhone should last on batteries, when people see the impact Flash has they may understand that the message isn't: "The iPhone doesn't last long on batteries.", but rather "Flash eats your battery."
(And yes, I suppose you could write flash that didn't eat batteries... but people don't.)