For those of you that have been patiently waiting - 7.4.1 is now live on Cisco.com
This release enables the 7.4 feature set for all FTD Devices (excluding those already EoS) as well as delivering additional feature capabilities and a tonne of improvements for both the latest as well as older hardware platforms.
Details as always in the release notes:
Cisco Secure Firewall Threat Defense Release Notes, Version 7.4.x - Features and Functionality [Cisco Secure Firewall Management Center] - Cisco