Yes @Mario Lopez, @Ambert, only the one contrib branch now - it wasn't making much sense to keep the old ones around as we only accept PRs against the active contrib branch anyway.
Bugfixes will generally get backported to 10. If you want to be absolutely sure yours will be backported before you start working on it then if you can outline the bug and a rough idea of the proposed fix in a draft PR or issue and mention (@) me and I'll make sure you get confirmation.