Propely the two things which have been postponed the most: BER and Brexit.
So the question is what will happen sooner?
The opening of Berlins new Airport BER (scheduled 2020
http://www.istderberschonfertig.de/)
The end of Brexit either by an actual hard or soft Brexit or withdrawing of leave notice.
Poll closes on December 12, 2019 the date of the UK General Elections.