Android 2.1 updates for the Sony Ericsson Xperia X8 have started to roll out, and no, SE didn't surprise anyone with Froyo. Android 2.1-update 1 is rolling out in stages, based on the "SI-number" located on the label on the back of your phone. Sony Ericsson has a list of all the SI-numbers that are being given the update now, and they will update that list accordingly. See the source link for the list.
Interestingly, SE again mentions that software updates are not under their complete control:
...the final timing of when each kit comes is depending on different local and global approvals and therefore we don’t really have a detailed plan per kit but rather release them as soon as all needed approvals are in.
All manufacturers need carrier approval for their software, but it appears the Sony Ericsson really wants us to remember that. If I can offer a suggestion -- stop shipping phones with Android 1.6 on them and you wont have to make so many excuses. Just sayin'. [Sony Ericsson Product Blog] Thanks Sam!