They release how they released back then. No additional difficulty. Blizzard made that clear.
You can check it here:
Wrath Classic 3.4.3 PTR Development Notes - In Development / Wrath Classic 3.4.3 PTR - World of Warcraft Forums (blizzard.com)
By default, the Heroic version of these dungeons will benefit from the additional rewards from Titan Rune Dungeons: Defense Protocol Gamma but will see no additional mechanics or difficulty adjustments as other dungeons are getting in Defense Protocol Gamma.