Will they though? It's not like you go around replacing nuclear plants every 10 years. Those things are built to last and they can stay operational for 5-6 decades at the very least. Say it's a particularly expensive plant that costs 10 billion eur to build. That's like 150 euros per citizen to keep the cheap electricity going for another 5-6 decades.

That said, France probably won't need to replace all their plants because by the time a lot of their plants are due for a replacement, renewables will have advanced far enough that the number of nuclear plants can be reduced without replacing them with fossil fuel burners. At which point France will take another step in their clean transition into renewables while Germany will have wasted valuable decades generating a metric fuck ton of CO2 that could have been avoided.