Well, I see two options. Subsidized or unsubsidized. For each one, there are a couple of possibilities, but if the rumors are true and our hopes become reality, the iPhone being unsubsidized and Cingular being good sports enough to give us some other form of subsidy for our contractual loyalty, then I'll be very happy.
If the announced prices are subsidized, we're f**ked. There is little or no chance of a highly-discounted data plan, especially like some are comparing to T-Mobile's Sidekick rate plans, mainly because the cost would be unimaginable for Cingular. The Sidekick doesn't consume "normal" web like the iPhone does, let alone have many other data features, rather routing websites and images through Danger's proprietary servers (much like AOL does, or did back in the day), to optimize speeds and data consumption. Most iPhone early adopters will not only be internet-savvy, high-end, heavy users, but the iPhone will likely sell out for a good 2-3 months, and that is a LOT of instant impact on their EDGE network. (It'll be, after 6-12 months, a lot of impact total on their network, I'm theorizing. A few million more new users than expected in a short time frame, even when it's only 2-4% of your established user base, could mean service level changes. Then again, they've been preparing for this for a while... so maybe not at all.) Anyhow, if this is the case, the iPhone v1 will go down as one of the most expensive non-celebrity-targetted smartphones ever, 4-8GB of flash RAM or not.
If the announced prices are unsubsidized, there's still a great chance of getting our money's worth for the 2-year-contract (assuming they really have no other option, which is consumer-unfriendly IMHO) through discounted service (rate plan for voice minutes or data usage). But some are theorizing 12-18 months of free service (voice and data), free data service, extremely discounted voice and data service... etc. You're all going to be sorely disappointed. The most they'll ever give is $150-200ish of subsidy for that 2 year contract, unless they SIGNIFICANTLY change their business model on overage (and not in the way you'd like), or sacrifice profit margins somewhere. So assuming there isn't an outrageous profit margin on data, a $25-40 data plan (unlimited, real internet on a smartphone average price between major 2.5-3G providers), the most they'll give is 6 months free internet, 12 months half-off internet, or 2 years 25% off internet, to add up to approximately the same subsidy they provide on new handsets with a 2-year-contract. Now, if there is an outrageous profit margin on data, I'm sure Cingular is so glad to have the iPhone buzz, multi-year exclusivity, and millions of new Apple customers that they'd sacrifice some or most of it, we could be looking at 2 years of half off current expected internet prices or more. This could finally make smartphone internet affordable.
The monkey throwing a wrench into all of it could be how Apple (or industrious hacker-propellerheads) handle laptop connectivity to share or distribute the internet.