There’s no doubt that the iPhone and other smart phones have put many carriers at the mercy of their users increase in usage. This is the famous problem that has happened again and again with AT&T over the years with users fed up with speeds far beneath what their phones are capable of. IOS 5′s rumored cloud features would magnify this problem and expose more weak areas in carrier’s 3G networks, but their 4G networks should be built to handle the increased workload. A 3G cell tower may have several 1.544Mbps T1 circuits working in tandem to provide what you currently see for speeds. A 4G cell tower should have at minimum a fiber link with up to 1 gigabit worth of bandwidth to measure up to the speeds capable by these devices. There is also of course the issue of backhaul at the carrier switching centers where you can still experience congestion. Carriers might not be thrilled to have a multitude of devices suddenly streaming all the data that’s currently stored on the device and seeing constant uploads of pictures and video from users instead of them doing this over their WiFi or being plugged into iTunes or other sync software. This increase will be especially painful on current 3G networks which will not see upgrades vs 4G networks that can be upgraded easier.
The other interesting thing that IOS 5 cloud features could provide is cheaper iPhones. A 16 gig phone can have a few hundred gigs of cloud storage making the more expensive phones a luxury most can do without and Apple may phase out larger phones to have users opt for a monthly payment for increased storage. Carriers currently hold the ball for the future. In fact making sure people have the fastest access ensures they’re off the air channel as fast as possible allowing spectrum to be re-used for other people. Limiting LTE only serves to clog the limited air interface with people taking longer than they should to download content, even streaming can be done in bursts.
Only Time Will Tell.