Included in these new releases is a dedicated extension to migrate custom URL aliases and URL history elements for existing 4.0.0 and 3.10.0 sites.

Please also note the security advisories which are resolved with these maintenance releases.
URL aliases

All of the fundamental problems with the multilingual URL alias system introduced in 3.10.0/4.0.0 have now been corrected. The ezurlaliasmigration extension in the distribution is provided to migrate custom URL aliases as well as the URL history elements (as long as the elements are not corrupted, possibly from earlier versions or bugs that were introduced in 3.10.0/4.0.0).

A feature pertaining to URL aliases has also been re-added. You can now specify whether a URL alias should be direct or redirect. Previously, all aliases were redirected (HTTP 301). Also, versions prior to 3.10 did not redirect URLs pointing to modules. With this new feature, this option is back.

Upgrading

When upgrading from 3.10.0 or 4.0.0, the process involves the bundled migration extension. Please refer to the upgrade documentation, which describes the steps in detail.
Future of 3.x community releases

The maintenance releases for 3.9 and 3.10 are likely the last ones for the eZ Publish 3.x series unless there are some serious issues that arise in the coming months. Current support contracts will remain valid. For new installations, eZ Publish 3.x is hereby deprecated and only 4.0.1 is recommended.
Future of 4.x community releases

A beta release of eZ Publish 4.1.0 should be announced soon.