As has been noticed, firmware version 4.33.19608 has been released. This should be going to all devices following Kobo's normal firmware roll-out schedule.
This release is largely fixes to the Kobo store. My notes from the beta have the changes as:
- Battery level for the newer devices handled better.
- Missing character prompt when reading MOBI.
- Removed highlight export limit for sideloaded epubs.
calibre
For calibre, there are no changes that will affect the drivers. The supported firmware version will be bumped in the next release of calibre. Until then, it is safe to use the "Attempt to support newer firmware" option in the driver.