If this thing's getting published by GenCon in August, don't you think the time for PHB playtests has passed?
I don't know if they have said they're going to playtest the DMG or the MM, but since those books come later, my speculation would "some material from those".
I recall an interview with Todd Kenreck where this was an indication from Crawford that there would be at least one playtest for both the
Monster Manual and
Dungeon Masters Guide.
I have been very surprised and delighted at how elegant and fun D&D 5th edition has been. I was beyond skeptical when they were preparing it around 2012-2013 that they would be able to come up with a version of the game that would bring people together as it has.
For that reason, I did not want to see yet another new edition of the game in 2024 because I find the endless tinkering with the rules after fifty years to be tedious. I prefer to see new stories, new options, new settings, and stuff like that.
That being said,
I have been pleasantly surprised with the revisions so far revealed (and, for the most part, very happy with where they have pulled back--giving the paladin a smite option for ranged weapons seemed very off to me in terms of color...I apologize if that steps on anyone's joy, don't want that, but I'm glad they pulled back from it)...and just over the moon that they are moving forward with 5th edition in terms of settings and stories and regarding this as a
revision to the three core books. For some that may be mere semantics, but for me it is an important shift in thinking that demonstrates a synergy of creative thinking, desire to draw from a decade of play experience, and yet a desire to build upon the foundation that has been established going forward.
Anyway, I think there will be a UA for each of the other core books. There may yet be one more PHG UA. 2024 should be a fun year.
Happy role-playing, everyone!