Those 13 IPs aren't as hard coded as you suggest. They typically ship with the DNS server software (ISC bind for example) but these are updated at regular intervals. As long as all 13 IPs aren't changed at once you could quite easily transition from one set of IPs to others. In ISC bind this root "cache" even has its own zone type; "hint".
Thanks, I wasn't aware they changed regularly. From what I can find, 4 v4 IPs have changed since 1997, plus the addition of a number of v6 IPs over the years. I'd be curious to know the last time all IPs were different, if ever.
