Or risk losing your Feedburner ID as Google does not reserve it for you.
I did not try to move my feed ID feeds.feedburner.com/pratham till as late as yesterday, and when I did, I found someone else (legit) had already taken it. The Google migration also fails since it doesn’t know what to do with two feeds pointing to the same ID.
I’ve written to Google and am awaiting their reply.
Update 12/Feb: Google seems to have fixed the problem, and I’ve moved to the new Feedburner.