The plan is to replace them with natural gas (https://www.tagesschau.de/wirtschaft/wirtschaft-155.html). At least until 2040, when they want to stop using natural gas (https://www.wiwo.de/politik/deutschland/regierungsbildung-ko...). After 2040, all fossil fuels and nuclear power are supposed to replaced by renewables. But no one knows how to do this yet, without any way to store significant amounts of energy.