Biggest problem facing airlines is APD and particularly because it's charged in each direction where as in Ireland it was only departing flights.
The UK will never scrap it as it's a money maker and traffic to/from UK airports is increasing so they would be mad to scrap it, it will take a decline in traffic for it to be looked at but they should only charge it one way not both ways.
A high chance Scotland will see it scrapped weather it goes independent or powers will be moved from London. At some stage there will be a change in Northern Ireland on it but no a chance in England and Wales.