Sorry for the German source, I couldn't find an English one.
Apparently, there are first talks between the German and French traffic ministers to expand the national railway tickets (49€ ticket on the German side, a soon-to-be equivalent in France) in the respecting neighbour country.
It's still a more than early stage, will take several years and will have to overcome the incompetency of Wissing, but the idea is intriguing.
Oh that's even better. Internal tickets are a good thing for vacation/"rail trip" if you're <28 but still too expensive.