During all the excitement of the 2009 Mobile World Congress, AT&T has quietly acknowledged that it should have a fully ready Long Term Evolution (LTE) network in 2011. AT&T has pledged in the past to introduce the 4G Network in 2010 but, according to Senior Architecture VP Kris Rinne, will see the first phase limited to trials in 2010, with commercial services available the following year. This will put AT&T's 4G Network about a year behind Verizon's 4G network, which is for trials later this year with commercial services planned for 2010.
AT&T doesn't seem too worried about Verizon's time line, maintaining that it can rely on HSPA+ and have the advanced 3G networks reach 20Mbps sometime later this year through software upgrades. The LTE network theoretically is at least five times as fast in downloads, about 100Mbps and has a lower latency that should make multi-layer games, VoIP, and two way calling more practical than on 3G networks.
Speaking of time lines, it's probably safe to say that Apple's future plans for the iPhone could well be a factor here. On the other hand, it's entirely possible that AT&T has no idea what Apple's plans are.