I added dynamically loading map objects or popup content. It works as in J3.
I noticed, that ajax loading is not works for File layers (KML/GPX and so on), it didn’t implemented in J3.
I hope in nearest month or two I will implement this feature and rewrite behavior for popup and hover text for this layers (not only from file, but also as it is done for simple lines, circles …)
I also rewrite all parts of extension to reuse my code (as it was done in J3)