Here’s a bit of a somewhat wild suggestion, implementing the MIT licensed OGRE 3D engine with Game Develop, maybe as an optional extension you can choose when installing Game Develop (as OGRE is around 130 MB). Have extra objects you can choose to add (3D model, 3D light, 3D sound) and possibly the ability to set the scene editors camera to a 3D camera if you have the OGRE extension enabled and installed.
I know it’s probably a crazy idea, but I’ll post it here anyway, just for the 
.
I wish that 4ian’s got the time to implement a 3D engine in to Game Develop so we can use it gorgeous event system to make 3D games,but I don’t expect that in the near future. 
At least not in full 3D to make any 3D games like FPS,TPS.
Though,it would be really good to have the possibility to use any 3D objects not only boxes and some lightmap generation maybe some realtime shadows so GD can have more potential in 2.5D game creation.I think it worth to put it on the To Do list,indeed 
But I would not expect more than 2.5D features.
There’s, according to my knowledge example of 3D walk engine (as 3D as Wolf3D was, except it support sloped walls), done from event side via some camera manipulation.
While I think 3D is out of scope of GameDevelop, if you want 3D engine with visual scripting, try CraftStudio. It isn’t free though, but pretty cheap (€20 now, which is VERY cheap for gamemaking software).