I'd say Vueling could merge into LEVEL in a few years time in order to consolidate iAG's low-cost operations, given that the two airlines are expected to codeshare on a number of routes. Gatwick could be a future base, though I predict Paris and Rome as the next operating bases, given Vueling's extensive operations from each airport.
I'm surprised that IAG haven't expand OpenSkies since it started operations - they've recently received a 767-300, but other than that there's no change in the destinations served. Post financial crisis I would have thought that Amsterdam would have been re-established, as well as Washington DC. Maybe the A321LR could play a role in future operations. Would be interesting to have IAG operating extensive premium, standard and low-cost networks out of Europe.