1.2 does not include any new features or important bug fixes. It is simply the change to runtime DLLs for map and tile setup data.
If you want this feature then you need to use the one from the Asset Store and existing projects will be broken - no way around that. I have moved the data related classes to a runtime DLL and Unity can not restore scripts on assets when this is done and that is why map and setup assets will be invalid.
If possible I suggest recreating the tile setup data and maps and use the new TileEd from asset store.
But if your project is far enough along then I can provide a special build where the data classes were not moved to the runtime DLLs. I think Unity 5.4 might throw an error in TileEd 1.1.7 because of new thread safety stuff they implemented. Not sure whether TileEd actually references the functions in plyLib which needed to be fixed for this.
I'll PM you with info on how to get the special build.