Hi Erlend and welcome to our forums!
There have been some thoughts about implementing glTF but for now it's not our priority. The format which is used by Blend4Web is similar in many ways (e.g it uses json/bin files to store metadata/binary arrays). However, there are many differences, mainly due to Blender-specific features, which our engine currently supports: blender animation keys, node materials, visual logic nodes, sophisticated combinations of material shading, etc.
We are going to support this important standard eventually, but first we need to rethink how these features can be implemented using glTF and refactor our code base to eliminate dependency on our internal format.
Thanks for the question!