You are right, support is still available till end of this year. They couldn't provide a solution because Gearbox won't be updated.
But.... Last night after trying few things got it working and the funny thing is that what it causes Gearbox not to work on Mavericks is not Gearbox itself but the latest driver with the added support for Mavericks. This is what I did:
To remove driver 7.3.6
1- On a terminal run this command sudo pkgutil --forget com.line6.driver.xtaudio.package (enter)
2- Then this sudo pkgutil --forget com.line6.driver.xtmidi.package (enter)
3- Reboot
To install driver 7.2.9
4- Downloaded driver version 7.2.9 http://line6.com/software/readeula.html?rid=5675
5- Run the 7.2.9 driver package to install it and ended the process with a reboot
After that Gearbox is working on Mavericks, at least that was my experience.
Hope this helps
Alexsnowflake's post in Pod X3 Live Usb Device Not Recognized was marked as the answer