Im going to guess that they are their own aircraft that they are just redeploying. I dont think Lufthansa has any more Airibus A380s on order. Some please correct me if im wrong thou.
I fly into Germany multiple times a year and Frankfurt has gotten to be the worst airport to fly into and clear customs. It is a maze of corridors and stairs. MUC on the other hand is new, clean ,efficient and easy to transfer. In the winter the SFO MUC route was an A 380 and a pleasure to fly. i am glad to see it go all year round.
Recently I was pleasantly surprised when I was booking a new flight (for November) to Munich from Miami and saw I would be on the 380. Previously, I believe a 330 was used. The last time I flew to Munich I had to go through Frankfurt. This is going to be great!