As posted above intercontinental flights work best with a hub. Lufthansa group already has two in Germany, and three more nearby if you count Brussels, Vienna and Zurich. Flights to other airline's hubs for example in the Middle East and USA will almost certainly be a feature of Berlin. But Lufthansa ditching Munich to hub and spoke in Berlin looks highly improbable, particularly as Munich is much closer to Italy which has been a major feeder of transfer passengers. The upside with SXF over TXL should be the integration of better onward travel links particularly long distance rail. TXL was pretty limited with only bus transport into the city or to the nearest underground station, which was a few kilometres away.