When TechTool Pro is updated, you will want to make sure that your Protogo devices are also updated.  

To do this, you will want to ensure that the copy of TechTool Pro used to create Protogo devices is up to date.  This can be located at:

/Applications/TechTool Protogo/Protogo Applications/

Open this copy of the app, and if it isn't already updated, choose 'Check for Updates...' from the TechTool Pro 6 menu, and the app will be updated to the latest version.  Now, all future Protogo devices will contain the latest version of TechTool Pro.

Updating existing devices depends on the profile used.  For the Intel and PowerPC profiles, you will need to re-create the device.  For Full Copy or Basic profiles, you can boot from the device and update TechTool Pro on the device itself using the update process described above.