I think the bulk of vacant jobs isn't low-skill anyway and even there you have a lot of robot-assisted work. Still it's unlikely that robots will fill the gaps at such a scale in the near future, possibly in four decades but not in this one or the next one. At short term, that's the next 1-1.5 decades we need a lot qualified migrants if we want to keep up. The government already had some immigration programmes running some years ago with mediocre success and lukewarm response. The idea was to get a lot of unemployed youth from countries such as Portugal, Spain, Greece, Bulgaria and Romania to come here. They underestimated their unwillingness to leave their countries especially with the high language barrier (C1+ since most Germans cannot speak English even at A1 level especially the older generations). This is why the economy had a few jubilating cries when thousands of refugees arrived. This is how desperate they actually are. The only young people who want to move to Germany for working are mainly IT workers and artists.
The other alternative is companies moving to countries with higher birthrate whilst the medium-sized business sector is shrinking (it's already shrunk drastically over the last 10 years). Whether that's what people prefer remains to be seen but seeing how people want both, zero immigration (even skilled ones) and zero native growth, I don't see they got much choice. This will have implications with price and cost development as well. I'd rather have skilled migrants than the possible alternatives but for that the government is lacking working programmes too.