Air Berlin posted a pre-tax loss of £28M in Q1 of 2007/08, compared to £21M for the same quarter last year, and so it seems unlikely that it would be prepared to undertake a major upheavel such as transferring its operation from STN to LTN at the present time.
Olney 1 Bravo is correct to remind us that even at LTN, early morning 'peak-time' slots are now becoming scarce (although LLAO could facilitate some limited additional airline ops during the early morning peak hours simply by further restricting corporate flights during this period [but such a move would not find favour with Harrods or Signature] through its slot allocation process with ACDL).
Additionally, any mass migration from STN to LTN might actually prove to be a 'two-edged sword' for LTN if it freed-up peak-time runway slots at STN.
Like others, my money's on another mainland Europe-based airline: but any substantial increase in arrivals into LTN during the 7am to 9am period would certainly put pressure on the already over-stretched London terminal airspace system.