I would be happy with:
1) Finalize Karma and make it on par with Mantra. Incorporate gpu where it make sense. As an artist I should have to create usd stage to see my scene. It feels like a separate software.
2) Optimize / fix the viewport
3) Don't forget Houdini quality of life features, working with graph, data visualization, better vex editor in general stuff to make procedural editing easier.
4) Revamped material system that’s integrated with cops and some painting tools (sim to substance stuff but with Houdini thinking)
5) Revamp curves (including curve editor, animation editor) and chops (user friendliness, speed etc)
6) Evolve fluids. Make it easier to use and artist controllable.
7) Further integration of dynamics like vellum with RBD
8) Continue to simplify and modernize the interface. Make the documentation artist friendly. I find a lot of the documentation feels like I’m reading a scientific paper and description of parameters does nothing to help to understand how they work. Instead of starting and stopping initiatives - finish them. For example - the videos that were supposed to walk us through all the nodes.
9) evolve interactive tools
10) evolve mid range tools like the labs. H18.5 brought some nice mid layer tools in the areas of pyro
11) Evolve kinefx - bring artist friendly animation tools but focus on where Houdini can add value. Maybe specialized character fx?