Firefox ESR doesn't supersede anything. It is a version of Firefox that receives some (not all) security fixes and is intended for Enterprise users to deploy across their organization.. It isn't interceded for home users or those without their own IT staff.

So, basically, Firefox latest (right now 13.0.1) is the most secure, stable and up to date. It is recommended for almost all users. ESR is a branch (right now based off Firefox 10) that isn't as stable or secure, but isn't update as much (nor is it supported). It will update to Firefox latest once a year, hold that version, and move steadily along those lines. (So it will be Firefox 17, then Firefox 24, etc.).

http://www.mozilla.org/en-US/firefox/organizations/faq/
https://wiki.mozilla.org/Enterprise/Firefox/ExtendedSupport:Proposal

ESR doesn't relate to any previous version of Firefox, it was a new concept which was "dreamed up" a month or so after Firefox 4.0 was released. ESR is intended for large organizations which have a large base of PC's to deal with.

Firefox 5.0 and later versions are on a 6 week update schedule vs the 42 week update schedule for ESR 10 and above. The next version is scheduled to be ESR 17 in November 2012.