I see they have managed to 'replace' the loss of DY next summer with DL to Boston. If BHX were as quick to 'replace' lost routes and carriers like this, we wouldn't be faring quite so badly.
Edinburgh is a totally different kettle of fish to Birmingham. The former is now a "real" capital city, since devolution, and thanks to events like the Edinburgh Royal Tattoo, and Edinburgh Festival has a very high profile for inbound tourism. Add to that North Americans who love to claim their Scottish ancestry and visit the old country, and you have all the ingredients to ensure the airport grows based on inbound governmental, business and leisure traffic in a way few airports away from London can do.
I can honestly only see two non London airports in UK getting real international / long haul traffic growth in the next decade or so, Edinburgh and Manchester. That's not to say the rest will stagnate, but they'll carry on doing what they do, shipping bucket and spaders to the usual places to toast for 2 weeks in the sun, and ferry business travelers via major European and middle eastern hubs.