Later in 2010, AT&T is planning to upgrade the 3G HSPA 7.2 network again. This time it will be upgrading to HSPA+, a standard that offers theoretical download speeds of 21 Mbps with actual download speeds averaging about a third of that figure. Eventually, AT&T will upgrade to a 4G technology called Long Term Evolution, or LTE. It will begin testing the technology later in 2010 with initial commercial deployments starting in 2011.
But upgrades to HSPA+ and 4G LTE will not affect iPhone performance since these phones do not have these technologies embedded.
Next gen. iPhone may be affecting by HSPA+ or LTE next year or two.