Can and will are two different things. Any phone running 2.1 should be able to handle 2.2 but most likely that update will come from the phone manufacturer which are notorious for a.) lagging behind, and b.) abandoning old phones. Even phones that were announced at release to be upgraded have since been abandoned, so unless you plan to flash a custom ROM, you should count on using the OS that comes with the phone at the time of purchase for a while.