I believe that now as a result of this election, Scotland will see more devolution pretty quickly with the large SNP influence in the Commons.
As for Wales, I can see APD being devolved among other relatively small scale duties etc. Devolving long haul APD at the moment probably has a very small income, so devolving it and effectively zeroing this tax in Wales will have a very minimal impact on the WAG's budget, whilst making CWL more attractive for those long haul carriers that wish to fly here.
IF (emphasis on 'if') APD was devolved to Wales on long haul flights, i think we would see a pretty instant return by TOM and perhaps another, whilst strengthening the case of a NYC route, despite the fact that BRS are 'very close' to getting one. Also, the CWL team have been in Dubai this week promoting Wales along with Visit Wales to the Arabian Travel Market, notably the only UK Airport to do so. The stature of this event should not be underestimated since all the MEB3 are present, along with potential visitors and would be users of any route offered to that region of the world. A great networking opportunity, and from what rhetoric has been passed around in recent months with regard to a route to that region, I would never say never ...