In my opinion as a business traveller it does not make sense for BA to drop Aberdeen - there is a market for the ABZ-LON route. I have travelled twice in the last two weeks (once weekend and once mid week) on either full or fairly full flights in both directions - paying in excess of $700 (return) for the pleasure for getting down to Heathrow (fares are similar with BMI).
Whilst companies are trying to push video conferencing, resticting business class travel in order to rationalise costs, people are still travelling; and the oil industry is not currently in recession - unlike other industries.
Also remember what BA did with Glasgow - BMI pulled out and BA are talking of 67 flights per week now. Obviously Aberdeen will not get the same attention, but in my opinion BA will maintain current schedules and probably increase capacity by switching 319s with 320s and 320s with 321s.