Two weeks ago I wrote that we had 40 "fixed" issues that cannot be closed until a change record is published for them. That number now stands at 39 issues as a result of churn from a few change records being written and a couple new issues fixed and tagged for a change record.
We have documentation about how to write a change record if you have not written one before.
If you start a change record and feel that you need input from the original issue authors, you can use the original issue queue to work out a draft just like jgSnell, SebCorbin and Cottser are doing in Remove first/last/odd/even classes in favor of CSS3 pseudo selectors.
Today is a great day to become involved with getting Drupal 8 to a stable release.