It appears that Sony Ericsson is about to make good on its promise of delivering the promised Android 2.1 upgrade for its XPERIA X10 lineup of devices by the end of Q3 According to a tweet from Sony Ericsson UK:
@KOR_9S We can only confirm that the upgrade to Android 2.1 is due for release before the end of September this year. We hope this helps.
It remains to be seen if this good news will be limited to UK customers or if the update will be pushed out in other markets (like Canada) at the same time.
All the X10 devices, namely the XPERIA X10 itself, the X10 Mini, and the X10 Mini Pro, are expected to receive the update.