Having used both Construct 2 and MMF2, I can say that the big thing that prevents me from using Construct 2, are the issues you encounter when it comes time to export. Granted, it is easier to actually make your games in Construct 2 than in MMF2/Fusion 2.5, but I'd honestly rather have to work around the things in Fusion, and have a much easier export time, than have an easier time making the games and having serious issues when exporting. Who knows if Construct 3 will fix those issues (hopefully it does), but the fact that Construct 3 is still going to be an HTML5 based engine, honestly puts me off.
I can understand completely why Clickteam wouldn't want to reveal their big features, given what Simon has already elaborated on. I'm very excited to see what Fusion 3 can do. I'll most definitely be buying Fusion 3 when it's released, as I do enjoy my Clickteam products.