Today, AT&T announced in a press release that changes are coming to its data plans for iPhone and iPad 3G users on 07/June/2010, as well as a tethering option. The $30 unlimited data plan is being replaced with two cheaper plans that impose restrictions to the amount of data users can consume per month.

The DataPlus plan, $15 per month, includes up to 200MB of data in a billing cycle. Users who exceed the 200MB limit during the month will be charged another $15 for each additional 200MB of data thereafter.

The DataPro plan, $25 per month, provides up to 2GB of data in a billing cycle. Users who exceed the 2GB limit during the month will be charged another $10 for each additional 1GB of data thereafter.

Both plans include unlimited usage of Internet access at AT&T WiFi hotspots. AT&T says it will assist users in tracking their data usage via text message alerts and through its MyWireless iPhone app.

AT&T claims that 98% of its customers will be covered under one of these two plans without going over the imposed limits. This statement seems somewhat suspect, however, as the communications giant has blamed its network congestion and other issues on the large volume of data being consumed by iPhone and other devices. If only 2% of users will be effected by this change in plans, it’s hard to imagine it will have any meaningful impact on service quality.

When Apple announced iPhone OS 3.0 last summer, it included a tethering option which has been available in many parts of the world since then. Despite promises to the contrary, AT&T never made the option available. Now, a year later and with the release of iPhone OS 4.0 looming, AT&T is finally offering tethering for iPhone users, but at a premium. Those AT&T customers who wish to allow their notebook or other devices to share their iPhone’s data connection will need to pay an additional $20 per month over and above their monthly data plan cost.

All of these changes go into effect next Monday, 07/June. It’s likely not a coincidence that Steve Jobs is scheduled to deliver his keynote on that day, which will undoubtedly include information on the release of iPhone OS 4.0 and the next iPhone hardware revision.