I have also been spending more time on the core of BlitzMax over the last year than I really intended to...
While it's disappointing the 3dmodule is some time off, I'm glad you are spending more time on the core of BlitzMax.
BlitzMax is a very impressive language, and to improve the core language (including 2d in 3d functions) I suggest would be a better use of your time. Let others build or wrap current 3d engines - or do what the PureBasic author has done and integrate a widely avaiable 3d engine.
The work on the current 3d engine could still perhaps be worked-on when you feel you could spare the time.
Why not ask people using BlitzMax what they think it lacks or what could be improved? Then concentrate your time on these suggestions - perhaps charging a reasonable amount for updates.