Hello Shankar,
I'm trying to imagine what you mean by auto-sync. I'm guessing your use case involves the latest members of the mainline or a devpath updating automatically triggering a sandbox to do a refresh. Is that what you are trying to do?
This could probably be done with a trigger script running off of configuration management events, but would likely involve writing your own custom trigger script to do so, or getting a Global Services engagement to write such a trigger script for you.
Regards,
Kael