Not officially announced, but according to @RFBurns the 7mate/7flix switch to MPEG-4 was apparently only the first step for a full MPEG-4 network. With 7QLD having 7, 7two, 7mate and now 7Bravo in HD only I feel like the same will happen to 7two in metro/ex. Prime7 areas.
His post here:
The way things are going I can see 7, 7two, 7mate, 7flix and 7Bravo in MPEG-4 HD only in all markets by 2025.