AT&T is ending unlimited internet options for both the iPhone and iPad, timed with the launch of the new iPhone on June 7th. Love it or hate it, a tactical mistake: they should have given new users more than 5 days to get grandfathered into unlimited plans: they would have been able to clear out a lot more soon-to-be-last-season 3G phones had they given customers say, 3 weeks notice.
This also indicates to me that there will be no CDMA iPhone announcement on June 7th. AT&T would not hamper themselves in a fight with a Verizon or Sprint iPhone assuming those carriers would offer it with an unlimited plan. Then again, AT&T is also going up against the EVO this weekend, probably the most significant challenger to the iPhone yet; the EVO will be the only phone on a 4G network (WiMAX) for at least several months. EVO plans will include unlimited WiMAX usage.
Existing iPhone and iPad customers will keep their plans. Pricing for new users, starting on June 7th, is $25/mo for 2GB + $10 each additional GB. iPhone users can also buy a 200mb monthly plan for $15 + $15 per additional 200mb.