There are many open source 3D engines in the form of library's and SDK's.
Like there are:http://www.delta3d.org/http://irrlicht.sourceforge.net/http://www.ogre3d.org/
Almost nothing needs to be coded from scratch to enrich Construct with 3D and 3D physics.
This if i understand this well. I am not a programmer.
I dont think that Ashley dont want to. Reading his last comments i have the feeling that he just has no time. And the 2d engine is not even out of Beta yet.
Jumping in his shoes, i dont see how he could manage all this, working on perfectioning the 2d shaders, and the events system, and the interfaces to it all, AND bring a 3D engine in something thats not stable yet.
But i do think that the future lays in bringing together construct and one of the open source 3d engines. Why re-invent water ? Its all done already, and its here as SDK's and C++ librarys.
So ? who's gonna do it ?