Construct 2 has much more complex dependencies than a document. Each part of a document is just text and formatting, and a conflict is obvious (either wrong text or wrong formatting). In Construct 2 you can have things like families, behaviors, family behaviors, and so on. Removing something like a family has a cascade of effects: several object types are affected; events relating to the family disappear; all references to the family behaviors must also be removed; and so on. If you press 'undo', all of this has to come back again. Just undo for a single user is a pretty complex problem to solve.
I'm not convinced any of the workarounds are very good: either you can't delete the object when you really intend to, and you first have to root out its dependencies and manually delete them which could be really time consuming, or you end up with ghost references everywhere without knowing why and you can't save or export the project until you clean everything up, which is a pain... and merging on save is like SVN
I think the feature is extraordinarily complicated to implement, and would not even be that practically useful. I think it's another case of a imagine-it-being-amazing-and-solving-everything feature request without taking in to account the practical likelihood that being able to collaborate in real-time simply allows you to contradict what someone else is doing simultaneously, and get in to a huge mess. I think you'd still have to learn to work on separate parts of the project at a time to avoid conflicts, and if you do that already with SVN, everything should merge smoothly. So no, this is not planned, I don't think it would ever work well enough to be worth dealing with the incredible implementation complexity, and you can already use source control solutions that work nearly as well with planning ahead. Instead I think it would help more to have other supporting features like modularity and as mentioned easier ways to merge existing projects.