easyJet is traditionally a very conservative airline. However, they have a clear (and well documented) strategy of becoming number one or number two at each of their bases. The Air Berlin deal was made to gain a greater foothold in the German market and explicitly to become number one in Berlin and specifically in BER, when it finally opens. The same can be said in MAN.
That is why 6 additional aircraft is not surprising. Whether that transpires to be the case with the slots having been returned to the slot pool, who knows.