Well, this is not a new idea, having an EU of two speeds or more is actually quite old. It even has an own Wikipedia article:
https://en.wikipedia.org/wiki/Multi-speed_Europe
And IMHO this is something I would not count on at the moment. The far right AfD in Germany is at the moment at an epic rise in polls of all states, and what they want it having a less powerful EU, where every nation can make more own decisions again, amongst other things.
Actually to quote their manifesto for the EP:
"Wir halten die EU für nicht reformierbar und sehen sie als gescheitertes Projekt. Daher streben wir einen 'Bund europäischer Nationen' an, eine neu zu gründende europäische Wirtschafts- und Interessengemeinschaft, in der die Souveränität der Mitgliedsstaaten gewahrt ist."
In English: We consider the EU to be unreformable and see it as a failed project. Therefore, we strive for a 'confederation of European nations', a new European economic and interest community to be founded, in which the sovereignty of the member states is preserved.
Even if this party is not in any power yet, these ideas most likely will become more influential in Germany over the next years.