EDIT: A Big update on this topic is presented with PS CC 14.2! Now you can have linked smart objects, it works like in InDesign. Just go to 'File → Place Linked' and choose your PSB file.
This is the Promo video from Adobe: https://www.youtube.com/watch?v=H6AIgoFDwlk
Is it possible to import a PSB file (saved smart object) into several PSDs, so when I edit the PSB the change is visible in every PSD?
I only get it that way, that the PSB is copied into the PSD and the source PSB remains untouched.