What I don't really know is what is driving that growth. My guess would be tourism and business, including the nascent hi tech sector. Good air connections are important for hi tech growth, as well as other businesses. So if Berlin wants to find a niche in the global hi tech world, it can't strangle its airports on the basis of green extremism. People will locate their venture businesses elsewhere, where key people can easily travel.
The growth factors you listed are exactly what's driving the growth for Berlin. I first and foremost would say, driver for growth number 1 are the low prices. Air travel is getting cheaper and cheaper and thus more people can travel. Also travelling (due to prices, availability, more routes, etc.) has become more of a commodity. Especially here in Europe, where distances (and thus again prices) are very low. Espeically for young people it's so normal now to make at least one weekend-trip to some European destionation every month. This doesn't only drive growth here in Berlin, but all over Europe (as well as in many other parts of the world), but it's a factor here, too.
Factor number two is that Berlin is getting "mature" regarding its econimical stance within Germany. Berlin and the east German states (former East German GDR territory) are still way poorer than the states in the former West, but especially Berlin (but also cities like Leipzig and Dresden) are slowly catching up. So while there is no real industry in Berlin, because all industries left Berlin after worldwar 2 towards West Germany (awway from the Russians), as you noted above, Berlin has a lot of hi-techn/IT companies, start-ups, service industries and also more and more headquarters, large company representations, as well as profit and non-profit organisations and agencies setting up camp here, mainly to be close to the federal government of Germany being close by.
Tourism is the third factor and is also growing every year. For a long time you had the feeling that new hotels were built on every corner in the city center. In 2018 Berlin saw over to 13 million tourists, with about 55% arriving by airplane. That's a growth close to 5% year on year. Another 10 million people came to town for congresses and exhibitions, which is a 2.5% growth year on year.
As you pointed out, all this is extremely dependent on air traffic. When AirBerlin went into insolvency in September/October 2017, hotel bookings in Berlin went down 6% immediately for the next four months until EasyJet had fully replaced AirBerlin here and started the operation from TXL in early/mid January 2018. And of course, all that businesses here, but also companies with HQs and organisations with international business are all reliant on working airports and a good network to all major cities in the EU and in the world.
A little part of me wishes that the BER terminal be preserved but never used, a monument to remind to future generations about politicians But my uninformed guess is that it will end up torn down and rebuilt, either from scratch with more gates, or using the foundations and rebuilding to the original plan with the old architects and contractors brought back, and the use of hard stands.
A fun idea. Not too bad actually. Would teach some people a lesson... ^^