I don’t think Ton has even weighed in on the work by Agoose77 and Mahalin, as their work is based on their own opinions on what an engine should look like and how it should be coded (and as a result creates uncertainty as to how much collaboration will take place).
Also, it was said back when that roadmap was introduced that it’s not a final decision and can change over time. Also, the difficulties with the .fbx export seems to indicate that the BGE is not going anywhere for the time being (because there’s no suitable alternative for painless game development with Blender).
A final note, the BGE has actually been in somewhat more than maintenance mode with the bugfixes and new functionality it has received, but how much at this point really depends on how much time the devs. have for coding. Also when it comes to authoring not being a priority, the new game publishing addon by Moguri debunks that idea.