Hi chrishilli,
you can safely update Taxi Booking to 3.11.3 on Joomla 3.4.0 now. We had to run a test to see if everything works fine on the new Joomla release and did not find any problems on our servers.
If anyone does spot a problem please submit a support ticket and we will take a look at it as soon as possible.
If you don't see the latest version in the Live update screen please click on "Refresh update information" to reconnect to the server and update should become available.
Hope this helps.
Best regards.