There's no timelime right now, after seeing how much HTC Hero owners are getting upset by not sticking to deadlines I guess SE are keeping their moths shut until they have a realistic sense of delivery.
You can check out what improvements Android 2.0 brings here. SE already included Bluetooth support, but I'd still like to see multiple account support and a few other things like camera flash and double-tap to zoom.
I sent an email to SonyEricsson asking about Android 2.1 update and they replied me there is no release date, but it'll be available soon. Let's keep waiting.
At the rate SE is delaying the much needed 2.0 2.2 has been announced let alone waiting for the 2.0 or 2.1 Wishful thinking perhaps SE is skipping the 2.0 & wait for the 2.2!!!! Thank you.