He... sorry for late to the party on this discussion...!
as a user of both programs I would have to agree that there is a very huge potential of having a Houdini engine integration on 3D coat. Like Aabel said, such an implementation would make it very easy for anyone to develop new "model" generators, depending on how the implementation is done.
To clarify, the Houdini engine API, in its current state, is a "geometry generator" (although you can use to statically trigger renders and image generation behind the scenes that output to files instead of to the host application). The high level concept is that the host application (i.e. 3D coat) provides "hooks" to pass geometry information into the API libraries for processing, then be able to fetch a geometry processed by the API.
The processing happens via "Digital Assets", which are encapsulations of functionality into a single module (which is, at its core, one of the main strengths of Houdini). Think of it as a generic data compositor, where the data processing is done via a combination of stock and scripted node networks, then encapsulated into a single node. The Houdini engine hooks allow the host application to load these "digital assets" as if they were native plug ins for live processing of geometrical data (either by providing a geometry input or simply generating geometry parametrically). Depending on how the connections are made between the host and the API, the implementation can take many forms to best fit the host application philosophy (i.e. in the case of 3DC, the digital asset parameters would become a "tool" ui, volumes could be an input and an output thanks to the Vox layers, etc)
Where this can be very powerful in 3D apps is that often, having some kind of parametric generator to start a model can be VERY useful (in addition to a means to process an existing model to, for example, add noises, effects, etc.) I think a good example of a digital asset is Kim Goossens road generator, which uses a single curve to generate a road based on rules (many of the 3DC tools can use curves as a parametric input.. there are very obvious parallels which can be drawn to some of these examples):
here is a very simple example of how to create a digital asset in Houdini (oldie but gets to the point)
in addition to the houdini engine running in unity (for a 3DC implementation, imagine similar concepts but more focused on setting up models for sculpting or adjusting sculpted models)
I feel this could be a huge advantage for 3D coat as it would be the first hires sculpting app to allow for such quick tool prototyping and development (i think you would have a lot of digital asset developers wanting to demo their tools in a hi res modeling app)