Sony Ericsson previously stated that the Xperia X10 would be stuck with Android 2.1 (Eclair) forever. Surprise, surprise. Gingerbread is on the way.
This is no rumor. According to the official Sony Ericsson Product Blog, the Xperia X10 will receive a staggering upgrade to Android 2.3 near the end of Q2 or early Q3. That's awhile away, but certainly worth the wait for anyone who stuck by the Xperia X10 for this long.
Note that the update will not be sent out over the air, and only PC-based users will be able to obtain it. Another caviat is that all personal settings and data will be lost during the upgrade process, so back up anything important first. The only safe spot will the memory card. And if for some reason you actually prefer Eclair over Gingerbread (that would only be acceptable for the actual desserts), you're stuck. No downgrading will be permitted.
So far there aren't any plans to upgrade the rest of the X10 family (the Xperia X10 mini, mini pro and Xperia X8) to Android 2.3.3. However, obviously things can change...at least at Sony Ericsson.