Yeah, I think HO is going to be prevalent; walls will have a hard time when they only have space for recovery/attacking move/support move. There's a lot less flexibility for them to run unique sets. That said, offense has a lot less coverage, which means that Pokemon with resistances to key type combos are going to be extremely useful (think Skarmory)
The only legitimately threatening setup sweepers are going to be those that get great coverage with their STAB(s). Others are walled far too easily because of their lack of powerful neutral coverage.
I predict that 3-Move non-choiced attackers will be moderately useful as well. I provide the example of Latios, who can run a powerful Draco Meteor/HP Fire/Surf set and get SE coverage on a lot of threats at the same time.