Releasing HVD in their next system would be like releasing Blu-Ray in 2003.
Ps2 and PS1 came out with formats that were already accepted to be the next big thing, that wasn't true when blu-ray launched. It wasn't until a while later that Blu-ray won the format war and started to see some mainstream penetration. By the time PS4 releases DVDs will still be > 50% marketshare i'd bet, why would they want to develop a new disc?
Maybe for PS5, because by then there is a possibility of higher resolution TVs. a format exclusively for games, which are the only things capable of utilizing a fraction of that space at this time, is stupid. A BLu-ray disc is sufficient space for any 1080P movie with all the loaded features, until their is another resolution bump i don't see a new format coming.