Let's never forget that DHK is above all a political animal, created with the intention of never having to rely on a single AOC for European lift. As such, should a Brexit result in UK based airlines losing their free and unhindered access to intra-EU flying, a UK AOC would no longer fulfil it's main objective.
My guess would be a transfer of assets to an EU based AOC. It will not be German, however, EAT Belgium might be revived for that purpose - they're building a brand new hub there as well. UK nationals without the right to work in the EU will, obviously, be adversely affected by such a move. The EMA hub might very well continue to operate, but on which scale will largely depend on what kind of customs deal the UK can land with the EU.