It's not possible to update your phone to 2.2 through an official update as Sony-Ericsson isn't going to update the Android OS any further (won't be updated passed 2.1).
That being said, you can still get 2.2 via a custom ROM on your phone but doing so will void any warranty you may have. I have a 2.2 custom ROM on my phone and I quite enjoy it as it adds a lot of functionality (and speed) to my phone.
Anyway, it's up to you whether you want to try this or not but make sure you know what you are doing before you attempt anything if you decide to try it so as to cause as few problems as possible.