As of December 31st, 2016, the 3rd generation MTi and Legacy Mode output mode will no longer be supported. The MTi 3rd and 4th generation are depicted below; 3rd generation have a product code that may be the following: MTi-28A53G35. Product codes of the 4th generation are shown as e.g. MTi-30-2A8G4.
The EOL of the 3rd generation has been announced in August 2013, the EOL notice can be found attached to this article. If you want to upgrade your 3rd generation MTi to a 4th generation version, the Xsens sales department can quote the upgrade. See the Xsens website for contact details and contact form.