I don't think one can compare a 3D engine and what you can do there with a 2D engine - or rather game creator - like Construct 2.
3D brings it's own set of challenges etc.
The choice is quite easy i think and I agree that you need to decide what game you want to make, look at the game creators and engines and then decide on one best suited.
If you want to make a FPS you are not goign to choose Construct 2 or GameMaker etc. even though technically you can make a Wolfenstein clone etc. Much better to use UE4 or Unity for that.
I think C2's competition is Gamemaker, Stencyl and Fusion 2.5 and much more likely Fusion 3 at the end of the year / early next year when they get a better .
Scirra decided to stick with HTML5. imho the mobile stuff will get sorted, a proper Steamworks plugin will be made one day
The arguments the OP gave for taking a break from Construct 2 is not really related to 3D. One of his points does highlight it but he lists:
Reason 1: C2 uses developing/unfinished technology - Well, tech always continues and its good to get in early sometimes
Reason 2: Limited commercial possibility - I don't think C2 limits the commercial possibility at all. In fact, it makes it more possible due to it being easy to create games.
All systems and game engines has its issues:
C2: Fantastic code system, and great price but performance / export lacking for mobile, No native export.
Stencyl: Great performance and code system, but terrible Ui (imho) and subscription price model.
Fusion 2.5: Great performance and powerful plugins but the click system is a bit weird and the UI feels very old. Lots of built in ceilings from older Multimedia Fusion. (this will be gone in Fusion 3.) Each exporter is paid for and not really cheap.
Gamemaker Studio: Click together scripting and code, but the click system is old and the Ui is not nearly as good as Scirra. Expensive exports, forums disjointed.
Unreal Engine 4: Free but takes 5% royalties after $3000, much more overhead to work on and much higher learning curve. Blueprints powerful but ideally coding will be needed
Unity: same as unreal more or less. Have to learn code to use it properly
So yeah...decide what you can and can't live with and make a choice. The OP did this for his reasons. We all will have our own reasons to stick with C2 or move on. At least we are all making games and thats fantastic.